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Alcohol and Alcoholism Effects on Brain and Development
Alcohol and Alcoholism Effects on Brain and Development Edited by
John H.Hannigan Wayne State University Linda P.Spear Norman E.Spear Binghamton University Charles R.Goodlett Indiana University Purdue University at Indianapolis
LAWRENCE ERLBAUM ASSOCIATES, PUBLISHERS Mahwah, New Jersey London
This edition published in the Taylor & Francis e-Library, 2009. To purchase your own copy of this or any of Taylor & Francis or Routledge’s collection of thousands of eBooks please go to www.eBookstore.tandf.co.uk. Copyright © 1999 by Lawrence Erlbaum Associates, Inc. All rights reserved. No part of this book may be reproduced in any form, by photostat, microfilm, retrieval system, or any other means, without prior written permission of the publisher. Lawrence Erlbaum Associates, Inc., Publishers 10 Industrial Avenue Mahwah, NJ 07430 Cover design by Kathryn Houghtaling Lacey Library of Congress Cataloging-in-Publication Data Alcohol and alcoholism: effects on brain and development/edited by John H.Hannigan…[et al.]. p. cm. Includes bibliographical references and indexes. ISBN 0-8058-2686-6 1. Alcohol—Physiological effects. 2. Alcoholism—Pathophysiology. 3. Brain—Effect of drugs on. 4. Fetal alcohol syndrome. 5. Developmental neuropsychology. 6. Neurotoxicology. [DNLM: 1. Brain—drug effects. 2. Brain—embryology. 3. Ethanol—adverse effects. 4. Ethanol —pharmacology. 5. Alcoholism—Damage, Chronic—chemically induced. 8. Maternal-Fetal Exchange.] QP801.A3A358 1998 618.3’268–dc21 DNLM/DLC 98–17719 CIP ISBN 1-4106-0295-8 Master e-book ISBN ISBN 0-8058-2686-6 (Print Edition)
List of Contributors
Introduction: How Research on Alcohol and Alcoholism Has Informed Research on Developing Brains John H.Hannigan, Linda P.Spear, and Norman E.Spear
1 Prenatal Exposure to Alcohol: Effects on Brain Structure and 1 Neuropsychological Functioning Tresa M.Roebuck, Sarah N.Mattson, and Edward P.Riley 2 Alcohol-Induced Brain Damage During Development: Potential Risk Factors 14 Wei-Jung A.Chen and James R.West 3 Modification of Alcohol-Related Neurodevelopmental Disorders: In Vitro 33 and In Vivo Studies of Neuroplasticity John H.Hannigan, Dwight E.Saunders, Loraine M.Treas, and Maureen A.Sperry 4 Temporal Windows of Vulnerability Within the Third Trimester Equivalent: 51 Why “Knowing When” Matters Charles R.Goodlett and Timothy B.Johnson 5 Prenatal Ethanol Exposure Alters the Modulation of the GABAA Receptor-Gated Chloride Ion Channel in Adult Rat Offspring 79 Andrea M.Allan and Daniel D.Savage III 6 Genetics, Psychomotor Stimulant Effects of Ethanol, and Ethanol 99 Absorption in Mice Bruce C.Dudek, Theresa Tritto, Kelly A.Case, Barbara J.Caldarone, and Jennifer Clarke 7 Rat Lines Selectively Bred for Alcohol Preference: A Potential Animal Model 118 of Adolescent Alcohol Drinking David L.McKinzie, William J.McBride, James M.Murphy, Lawrence Lumeng, and Ting-Kai Li 8 The Alcohol Deprivation Effect: Experimental Conditions, Applications, and 142 Treatment Charles J.Heyser, Gery Schulteis, and George F.Koob 9 The Transfer of Alcohol to Human Milk: Sensory Implications and Effects 157 on Mother-Infant Interaction Julie A.Mennella 10 The Role of Fetal and Infantile Experience With Alcohol in Later 177 Recognition and Acceptance Patterns of the Drug Juan Carlos Molina, Héctor Daniel Domínguez, Marcelo Fernando López, Marta Yanina Pepino, and Ana Eugenia Faas 11 Covering All Bases: Engaging and Treating Individuals With Alcohol Problems 202 Jane Ellen Smith, Robert J.Meyers, and V.Ann Waldorf
vi Contents 12 Future Research on Alcohol and Development: Forging a Merger of 219 Discovery and Application Charles R.Goodlett Author Index
List of Contributors Andrea M.Allan, Department of Neurosciences, University of New Mexico, Health Sciences Center, 915 Camino de Salud, NE, Albuquerque, NM 87131–5223 Kelly A.Case, Department of Psychology, State University of New York at Albany, 1400 Washington Avenue, Albany, NY 12222 Barbara J.Caldarone, Department of Psychology, State University of New York at Albany, 1400 Washington Avenue, Albany, NY 12222 Wei-Jung A.Chen, Department of Human Anatomy & Medical Neurobiology, Texas A&M University College of Medicine, Health Science Center, 228 Reynolds Medical Building, College Station, TX 77843–1114 Jennifer Clarke, Department of Psychology, State University of New York at Albany, 1400 Washington Avenue, Albany, NY 12222 Héctor Daniel Domínguez, Center for Behavioral Teratology, San Diego State University, 6363 Alvarado Court, #209, San Diego, CA 92120 Bruce C.Dudek, Department of Psychology, State University of New York at Albany, 1400 Washington Avenue, Albany, NY 12222 Ana Eugenia Faas, Instituto de Investigacion Medica, M.M.Ferreyra, Casilla de Correo 389, Cordoba 5000, Argentina Charles R.Goodlett, Department of Psychology, LD124, Indiana University—Purdue University at Indianapolis, 402 North Blackford Street, Indianapolis, IN 46202–3275 John H.Hannigan, Department of Obstetrics & Gynecology, Wayne State University School of Medicine, C.S.Mott Center for Human Growth & Development, 275 East Hancock, Detroit, MI 48201 Charles J.Heyser, Department of Psychology, Franklin and Marshall College, Lancaster, PA 17604–3003 Timothy B.Johnson, Department of Psychology, LD124, Indiana University—Purdue University at Indianapolis, 402 North Blackford Street, Indianapolis, IN 46202–3275 George F.Koob, Department of Neuropharmacology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037 Ting-Kai Li, Department of Medicine, Indiana University School of Medicine, Emerson Hall 421, 545 Barnhill Drive, Indianapolis, IN 46202–5124 Marcelo Fernando López, Instituto de Invesitigacion Medica, M.M.Ferreyra, Casilla de Correo 389, Cordoba 5000, Argentina Lawrence Lumeng, Department of Medicine, Indiana University School of Medicine, 975 West Walnut Street, IB 424, Indianapolis, IN 46202–5124 Sarah N.Mattson, Center for Behavioral Teratology, San Diego State University, 6363 Alvarado Court, #209, San Diego, CA 92120 William J.McBride, Department of Psychiatry, Institute of Psychiatric Research, Indiana University School of Medicine, 791 Union Drive, Indianapolis, IN 46202–4887 David L.McKinzie, Department of Psychiatry, Institute of Psychiatric Research, Indiana University School of Medicine, 791 Union Drive, Indianapolis, IN 46202–4887 Julie A.Mennella, Monell Chemical Senses Center, 3500 Market Street, Philadelphia, PA 19104–3308
viii List of Contributors Robert J.Meyers, University of New Mexico, Center on Alcoholism, Substance Abuse and Addictions (CASAA), 2350 Alamo Street, SE, Albuquerque, NM 87106 Juan Carlos Molina, Instituto de Investigacion Medica, M.M.Ferreyra, Casilla de Correo 389, Cordoba 5000, Argentina James M.Murphy, Department of Psychology, Indiana University—Purdue University at Indianapolis, 402 North Blackford Street, Indianapolis, IN 46202–3275 Marta Yanina Pepino, Instituto de Investigacion Medica, M.M.Ferreyra, Casilla de Correo 389, Cordoba 5000, Argentina Edward P.Riley, Department of Psychology, Center for Behavioral Teratology, San Diego State University, 6363 Alvarado Court, #209, San Diego, CA 92120 Tresa M.Roebuck, Center for Behavioral Teratology, San Diego State University, 6363 Alvarado Court, #209, San Diego, CA 92120 Dwight E.Saunders, Department of Obstetrics & Gynecology, Wayne State University School of Medicine, C.S.Mott Center for Human Growth & Development, 275 East Hancock, Detroit, MI 48201 Daniel D.Savage III, Department of Neurosciences, University of New Mexico School of Medicine, Albuquerque, NM 87131–5223 Gery Schulteis, Department of Anesthesiology, VAMC School of Medicine, University of California at San Diego, 3350 La Jolla Village Drive, San Diego, CA 92161–5085 Jane Ellen Smith, Department of Psychology, Logan Hall, University of New Mexico, Albuquerque, NM 87131 Linda P.Spear, Department of Psychology, Center for Developmental Psychobiology, Binghamton University, State University of New York, Binghamton, NY 13902–6000 Norman E.Spear, Department of Psychology, Center for Developmental Psychobiology, Binghamton University, State University of New York, Binghamton, NY 13902–6000 Maureen A.Sperry, Department of Obstetrics & Gynecology, Wayne State University School of Medicine, C.S.Mott Center for Human Growth & Development, 275 East Hancock, Detroit, MI 48201 Loraine M.Treas, Department of Obstetrics & Gynecology, Wayne State University School of Medicine, C.S.Mott Center for Human Growth & Development, 275 East Hancock, Detroit, MI 48201 Theresa Tritto, Department of Psychology, State University of New York at Albany, 1400 Washington Avenue, Albany, NY 12222 James R.West, Department of Human Anatomy & Medical Neurobiology, Texas A&M University College of Medicine, Health Science Center, 228 Reynolds Medical Building, College Station, TX 77843–1114 V.Ann Waldorf, Veterans Affairs Medical Center, 2100 Ridgecrest Drive, SE, Albuquerque, NM 87110
Introduction: How Research on Alcohol and Alcoholism Has Informed Research on Developing Brains John H.Hannigan Wayne State University Linda P.Spear Norman E.Spear Binghamton University
In theory, basic research on questions in the biomedical or biobehavioral sciences, such as how cells grow, or how neurons communicate biochemically, or how infants learn, provides the knowledge with which “real-life” problems can be solved. The knowledge is applied to the problems. In theory, research directly on clinical problems, such as abnormal cell growth, or alcoholism, or mental retardation, spawns methods and models and information that each illuminate the foundations of biology, physiology, and psychology. Solving problems leads to knowledge. In practice, both efforts in science operate simultaneously. Ideally, the basic and the clinical complement, inform, and facilitate each other. This volume is an example of how well that interaction between basic and clinical research works. The questions and problems concern brain development and early learning, fetal alcohol effects, the acquisition of responses to alcohol, and alcoholism treatment. Because these are all very complex questions and problems, the answers and research are complex as well. In general, the chapters form a well focused collection of both human-clinical (chapters 1, 9, & 11) and basic-animal research (chapters 2 through 8 & 10). The research is both multidisciplinary and interdisciplinary. The chapters are organized along several dimensions including ontogenetic, biobehavioral, and mechanistic aspects of responses to alcohol. In overview, chapters 1 through 5 discuss fetal alcohol effects; chapters 6 through 10 discuss factors affecting responses to alcohol, especially in young organisms (chapters 9 & 10); and chapter 11 describes community interventions for treatment of alcoholism. An important recurring theme common to chapters 2 and 4 through 7 is analysis of genetic factors that influence the neural and behavioral responses to alcohol. The first five chapters present new research that draws a sharp focus on several of the defining principles of the field of teratology, in general, and of neurobehavioral teratology, in particular. Using studies of the effects of prenatal exposure to alcohol in humans and animals (in vivo models) and in tissue culture (in vitro models), the topics of these chapters serve as excellent examples of Wilson’s principles applied to neurobehavioral teratology as defined by Vorhees (1986), including the principles of teratogenic response, of genetic and environmental determination, of specific mechanisms, target access (or critical organ), critical periods, and dose-response relationships. Furthermore, chapters 2, 3 and 4 illustrate the functional interrelatedness of mechanism(s) and critical periods for particular target tissues—even specific brain regions—in defining risk for teratogenesis.
Introductions xi Chapter 1 (Roebuck, Mattson & Riley) describes the state-of-the-art in our understanding of the relationships among structural central nervous system (CNS) abnormalities and neuropsychological dysfunction in children with fetal alcohol syndrome (FAS). In addition to providing a cogent clinical description of FAS as background for chapters 2 through 5, this research presents evidence that some CNS areas in children appear more sensitive to the teratogenic impact of alcohol than others (principle of target access and principle of teratogenic response). It is valuable to recognize in this chapter the role that basic-animal research played in defining the neurobiological and behavioral hypotheses assessed in the clinical research (cf. Hannigan, 1996). That continuing influence of basic research, by Riley and his colleagues and others, reflects a key feature of this volume as a whole: that of basic research informing clinical studies. Chapter 2 (Chen & West) reports on risk factors associated with fetal alcohol effects. The authors review studies assessing the influence of co-drug use and other constitutional and behavioral factors that increase the risk for fetal alcohol effects in rodents (principle of genetic and environmental determination). Chen and West review evidence that the patterns of maternal alcohol consumption (how much is drunk and when), as well as parental genetics (varying rodent strains) and poly-drug exposure (e.g., perinatal cocaine), increase the magnitude of neurobehavioral fetal alcohol effects. Recognizing such risk factors may give clues to the mechanisms of alcohol teratogenesis, as well as suggest potential treatments and means of prevention. In chapter 3, Hannigan, Saunders, Treas, & Sperry examine studies assessing pharmacological and environmental treatments for fetal alcohol effects in rats. Diminished CNS responses to environmental enrichment suggest that prenatal alcohol exposure produced enduring alterations in neural plasticity in vivo. The authors propose a general hypothesis about the neural mechanism(s) contributing to diminished neural plasticity (principle of specific mechanisms), and use in vitro techniques to examine the roles of neural growth factors (e.g., retinoic acid and GAP43/B50) in fetal alcohol effects. Chapter 4 (Goodlett & Johnson) can be viewed as a treatise on the principle of critical periods. Indeed, this research shows how susceptibility of specific areas within the CNS (principle of target access), depends on when during CNS maturation the alcohol exposure occurs. Goodlett and Johnson argue that critical periods can be defined systemically by understanding how the cellular mechanisms of teratogenesis change over time. Allan and Savage (chapter 5) detail their research on one potentially critical aspect of dysfunctional neurobiology after prenatal alcohol exposure: the profound effects on GABAA receptors. Allan and Savage take advantage of the fact that genetic differences in the expression of GABAA receptor subtypes is well-defined, and that the pharmacology of these receptors is well-characterized, to assess the contribution of GABA stimulation or excitation to enduring neurobehavioral dysfunction in prenatal alcohol-exposed offspring. These results may also be a clue to potential pharmacological therapies for fetal alcohol effects. The next three chapters (chapters 6–8), continuing in part from the groundwork laid in chapter 5, discuss the genetic, ontogenetic, neural, and behavioral influences on responsivity to alcohol. These studies bear on clinical issues in the development of alcoholism by investigating the factors affecting the initiation and maintenance of alcohol
xii Introduction drinking, as well as the factors affecting the reinitiation of drinking after brief periods of abstinence. Clues from basic research in these areas may prove vital in devising effective clinical treatments for alcoholism and relapse. Chapter 7 (McKinzie, McBride, Murphy, Lumeng, & Li) presents a series of studies assessing differences in biobehavioral responses to challenge doses of alcohol in rats bred for differential preferences for consuming alcohol, that is the alcohol-preferring (P) and non-alcohol-preferring (NP) rats, and low alcohol drinking (LAD) and high alcohol drinking (HAD) rat lines. This new research assesses these line-dependent differences in alcohol preference in adolescent animals, an age of heightened susceptibility to the psychotropic effects of alcohol and other drugs. Analogous to the critical periods analyses by Goodlett and Johnson in chapter 4, studies of the type used by McKinzie and colleagues illustrate how systematic evaluation of line- and age-dependent pharmacologic responses can provide insights into the processes and factors affecting initiation of alcohol drinking behavior. In contrast to alcohol preferences in rats, the research described in chapter 6 by Dudek, Tritto, Case, Caldarone, and Clarke targets a different response to alcohol—the biphasic, dose-dependent activational effects of acute alcohol doses in mice. These authors assessed locomotor activation in several strains of mice to assess the genetic bases of differential responses to these effects of alcohol. The combination of choosing a precisely defined behavioral-biological response to alcohol and a sophisticated genetic analysis allows estimation of the numbers of genes controlling CNS effects of alcohol, and forms the basis (and justification) for other ongoing gene mapping research using quantitative trait loci (QTL) techniques. Heyser, Schulteis, and Koob (chapter 8) describe an animal model assessing a critical aspect of alcoholism: the enhanced response to a first drink after a period of abstinence. The exaggerated magnitude of this response to a first re-exposure to alcohol, called the “alcohol deprivation effect,” may explain the great risk people with alcoholism face in trying to drink socially or intermittently. As in chapter 7, a developmental analysis is used to help analyze the phenomenon. The next two chapters can be viewed as integrating two earlier themes in this volume: prenatal alcohol exposure and early responses to alcohol. How does fetal or early infant exposure to alcohol affect later responsivity to alcohol? In chapter 9, Mennella discusses research on the behavioral sensitivity of human infants to very small levels of alcohol in breast milk. This sensitivity appear to be mediated by responses to the altered sensory qualities of the milk (i.e., alcohol-adulterated odor and/or taste). Mennella’s research results imply that even very young infants will learn something about alcohol even when exposed to low, nonpharmacological levels. In chapter 10, the research by Molina, Domingues, López, Pepino, and Faas with rats suggests that fetuses and infants given early experience with the sensory qualities of alcohol can learn a preference for alcohol. These authors review an extensive series of studies using an animal model assessing the same issues raised by Mennella and that detail the impact of nonpharmacologic levels of alcohol exposure during the prenatal and early neonatal periods. These exposures can increase subsequent alcohol intake and affect later learning involving alcohol. In chapter 11, Smith, Meyers, and Waldorf compare the features of three comprehensive alcoholism treatment regimens incorporating brief motivational enhancement therapies, together with direct community and/or family involvement in the treatment. The strategies described by Smith and her colleagues are relevant to a wide number of substanceabusing populations, including pregnant women and adolescents.
Introductions xiii Finally, in the concluding chapter, Goodlett describes his vision of the potential future directions and value of multidisciplinary work that is energized by effective communication among basic and clinical researchers. This volume began as a symposium at Binghamton University in June 1996. Almost all of the primary authors trained as graduate students or postdoctoral fellows at Binghamton University during the last 20 years, or had trained with current Binghamton University faculty at other institutions. Although there was a tradition of alcohol research at Binghamton University, particularly regarding behavior genetics, the confluence of eventual interest in alcohol research for many of these authors was not by some grand design. These scientists, trained in varied disciplines at Binghamton and elsewhere, all chose over the years to bring their multidisciplinary approaches to bear on Alcohol and Alcoholism: Effects on Brain and Development.
ACKNOWLEDGMENTS We appreciate the expert assistance of Anissa English, Bernadette Cortese, and Surilla Randall in preparing the book and the indexes.
REFERENCES Hannigan, J.H. (1996). Of mice and women and alcohol: A fractal history of fetal alcohol syndrome research. Developmental Psychobiology, 29, 398–400. Vorhees, C.V. (1986). The principles of behavioral teratology. In: E.P.Riley & C.V. Vorhees, (Eds.), The Handbook of Behavioral Teratology (pp. 23–48). New York: Plenum Press.
Alcohol and Alcoholism Effects on Brain and Development
1 Prenatal Exposure to Alcohol: Effects on Brain Structure and Neuropsychological Functioning Tresa M.Roebuck Sarah N.Mattson Edward P.Riley San Diego State University
Prenatal alcohol exposure can have devastating and long-lasting effects on the exposed individual. These effects include physical anomalies and cognitive and behavioral impairments with outcomes ranging in severity from perinatal death to subtle behavioral problems. One clearly defined outcome of heavy prenatal alcohol exposure is fetal alcohol syndrome (FAS), which is characterized by pre- and/or postnatal growth deficiency, craniofacial anomalies, and evidence of central nervous system (CNS) dysfunction (Jones & Smith, 1973). It is estimated that FAS affects approximately 0.29 to 0.48 per 1,000 live births, with incidences increasing to 2.99 per 1,000 in certain socioeconomic and ethnic groups (Abel & Sokol, 1991). Importantly, these estimates include only the subset of alcohol-exposed individuals who meet the clinical criteria for a diagnosis of FAS. They do not include persons exposed to alcohol prenatally with some, but not all, of the effects required for a diagnosis of FAS. Although this second group of individuals may not display all or any of the physical features of FAS, they often exhibit behavioral and cognitive impairments very similar to those seen in “full blown” cases of FAS. Therefore, the impact of prenatal alcohol exposure may be more subtle and far-reaching than once believed. The behavioral and cognitive impairments seen in individuals with FAS are most likely the manifestations of underlying structural or functional changes in the brain. However, the specific relationship between brain pathology and behavioral and cognitive alterations in these children is still unclear, highlighting the necessity for a more thorough understanding of alcohol’s specific effects on brain and behavior. Additionally, because the threshold for alcoholrelated effects is not known and because some of these effects may be extremely subtle (e.g., Goldschmidt, Richardson, Stoffer, Geva, & Day, 1996), it is important to elucidate the pattern of brain anomalies and behavioral and cognitive deficits in alcohol-exposed children, both with and without the diagnosis of FAS. Recent data obtained using brain imaging and neuropsychological testing are helping to clarify the specific nature of these anomalies. This chapter summarizes recent work from our laboratory using magnetic resonance imaging (MRI) and neuropsychological testing to examine groups of children with FAS and, where applicable, groups of children with histories of heavy prenatal alcohol exposure but without the full syndrome of FAS. These children are referred to here as having prenatal exposure to alcohol (PEA).
2 Alcohol and Alcoholism NEUROANATOMICAL FINDINGS Animal models provided much information about alcohol’s specific effects on the brain (see Miller, 1992 for an overview of this research). However, research with these animal models may have limited generalizability to humans, leaving much to be learned about how alcohol uniquely affects the developing human brain. Much of the earliest information about alcohol’s effects on the human brain came from autopsy reports of children with FAS. These children were exposed to heavy amounts of alcohol in utero and usually died due to complications resulting from this exposure. Jones and Smith (1973) published the first report of an autopsy on a child with FAS. Their results revealed microencephaly and a uniformly thinned and disorganized cortex underlying a massive neuroglial leptomeningeal heterotopia. Additionally, the corpus callosum and other midline commissures were absent, and the cerebellum was underdeveloped and poorly formed. Since this initial report, there have been about 25 additional autopsy reports in the literature. (For a detailed review of these studies, see Clarren, 1986, and Mattson & Riley, 1996). In general, these subsequent reports of autopsied brains documented a wide range of structural problems, the most common being microencephaly and malformations, consistent with a failure or interruption in neuronal migration (Clarren, 1981). However, there was extreme variability in the types of abnormali-ties found in these brains; thus the basic conclusion from these studies was that there is no specific pattern of brain malformation that occurs following prenatal alcohol insult (Clarren, 1986; Peiffer, Majewski, Fischbach, Bierich, & Volk, 1979). However, it should be noted that there are limitations in using these studies to generalize to the larger population of individuals with FAS. First, these autopsy studies reflect a skewed sample of only very severe cases of children with FAS. Furthermore, although no obvious pattern of brain deficits was found, autopsy studies may not be sensitive or systematic enough to detect a more subtle pattern of brain abnormalities. More recently, MRI techniques allowed researchers to learn about the brains of surviving children with FAS. Because MRI analysis is safe and noninvasive, it allows researchers to compare specific brain structures in individuals with histories of prenatal alcohol exposure to those of other normally and abnormally developing persons. Although clinical assessments of these images often do not reveal obvious structural abnormalities, the use of more detailed quantitative analysis allows researchers to examine specific brain structures, determine their volumes, and systematically compare them to brain structures in normal subjects. The use of MRI combined with quantitative analysis is bringing researchers closer to understanding the nature of alcohol’s effects on the developing human brain. Recent work in our laboratory examined the effects of heavy prenatal alcohol exposure on specific brain structures. Although the amount of alcohol that our subjects were exposed to in utero is difficult to quantify, the mothers of these children would typically be classified as abusive drinkers; that is, they drank excessive amounts of alcohol in a fairly regular or binge drinking pattern throughout their pregnancies. Our MRI studies revealed reductions in the volumes of both the cerebral and cerebellar vaults and increases in the cortical and subcortical fluid in children with FAS when compared to nonexposed children (Mattson & Riley, 1996). These findings suggest an overall decrease in the development of brain tissue in children prenatally exposed to alcohol. Detailed results of these MRI studies follow.
Prenatal Exposure to Alcohol 3 Corpus Callosum As determined by both autopsy and MRI studies, the developing corpus callosum appears to be particularly sensitive to the effects of alcohol. This structure, which is composed of 200 to 800 million nerve fibers, is the major connection between the neocortical hemispheres. It processes interhemispheric information and provides interhemispheric cooperation necessary for actions and movements of the body (Kolb & Whishaw, 1990). FAS autopsy reports detailed cases of complete agenesis or absence of the corpus callosum (Jones & Smith, 1973; Peiffer et al., 1979; Wisniewski, Dambska, Sher, & Qazi, 1983), partial agenesis (Kinney, Faix, & Brazy, 1980), and cases with a significantly thinned but present corpus callosum (Clarren, Alvord, Sumi, Streissguth, & Smith, 1978; Coulter, Leech, Schaefer, Scheithauer, & Brumback, 1993). Additionally, the anterior commissure, which forms a second, much smaller pathway between the right and left cerebral hemispheres, was reported to be missing in some cases (Clarren et al., 1978; Peiffer et al., 1979) and underdeveloped in another case (Coulter et al., 1993). MRI studies provided more information about the specific areas of the corpus callosum that are affected by prenatal alcohol exposure, along with additional data about the frequency of callosal agenesis in children with FAS. The incidence of agenesis of the corpus callosum found in the general population is 0.3% and in other developmentally delayed populations is 2.3% (Jeret, Serur, Wisniewski, & Fisch, 1986; Jeret, Serur, Wisniewski, & Lubin, 1987). In our initial MRI study examining brain structures in children with FAS within our limited sample of individuals in San Diego, we reported one child with a moderately hypoplastic corpus callosum and another with agenesis of the corpus callosum (Mattson et al., 1992). A subsequent MRI study, specifically looking at abnormalities of the corpus callosum, found another case of agenesis and mentioned a third case that although not evaluated for that study, was known to have callosal agenesis (Riley et al., 1995). At the time that study was conducted, 44 alcohol-exposed individuals in the San Diego area had been evaluated, providing an agenesis incidence rate of nearly 7%. In addition, Jeret and Serur (1991) speculated that prenatal alcohol exposure might be a leading cause of corpus callosum agenesis. More recently, Johnson, Swayze, Sato, and Andreason (1996) examined nine cases of FAS, and agenesis of the corpus callosum was noted in three. In our study, we examined the size of the corpus callosum in 10 children with either FAS or PEA by measuring the overall midsagittal area along with the area for each of five equiangular regions. These children were found to have reductions in the overall area and in four of the five equiangular regions when compared to matched controls. Because children with FAS are typically microcephalic, overall brain size was controlled for to determine if the reductions seen in the corpus callosum were disproportionate to the reductions seen in the rest of the brain. Three of five regions remained significantly different from those in control subjects after accounting for overall brain size. These affected areas correspond approximately to the genu (which links the prefrontal areas), the portion of the corpus callosum just anterior to the splenium (which primarily links sensory areas), and the splenium (which primarily links the visual areas) (Kolb & Whishaw, 1990). Interestingly, these results are similar to those found in a separate MRI study examining the corpus callosum in children with attention deficit hyperactivity disorder (Hynd et al., 1991). These callosal anomalies might be related to the behavioral similarities (e.g., hyperactivity, impulsivity, and attentional difficulties) reported between these two groups of children.
4 Alcohol and Alcoholism Basal Ganglia The basal ganglia are a collection of nuclei whose primary input comes from the cerebral cortex, with output directed through the thalamus and back to the prefrontal, premotor, and motor cortices. These structures are traditionally considered part of the motor system, although they may also play a role in some forms of cognitive functioning (Côté & Crutcher, 1991). Furthermore, diseases with known pathology in these areas (e.g., Parkinson’s disease and Huntington’s disease) frequently have cognitive components (Cummings & Benson, 1992). Autopsy studies of children with FAS reported several cases with evidence of damage to the basal ganglia (Peiffer et al., 1979; Ronen & Andrews, 1991; Wisniewski et al., 1983). MRI studies specifically examining the basal ganglia and diencephalon revealed that these areas may be especially sensitive to the teratogenic effects of alcohol. A study examining children with FAS found reductions in the size of the basal ganglia and diencephalon, even after controlling for overall brain size (Mattson et al., 1992). A subsequent MRI study examining the basal ganglia and diencephalon in two children with PEA found similar reductions in the volume of the basal ganglia as well as in the diencephalon, although when brain size was accounted for, the volume of the diencephalon was similar in comparison to nonexposed controls (Mattson et al., 1994). These results suggest that the basal ganglia, like the corpus callosum, may be especially sensitive to the effects of alcohol exposure in utero. These results also support the notion that specific brain structures might be more susceptible to anomalous changes than others, and that brain changes can occur in the absence of the facial features on which a diagnosis of FAS is dependent. A subsequent study examined six children with FAS and again found that the basal ganglia and diencephalon were reduced when compared to nonexposed controls. Follow-up analyses, dividing the basal ganglia into the caudate and the putamen, found that these structures were also reduced. However, when overall brain size was accounted for, the basal ganglia, and, more specifically, the caudate were the only structures that remained significantly reduced in volume in the FAS children (Mattson, Riley, et al., 1996). In contrast to the earlier study of children with FAS (Mattson et al., 1992), the diencephalon was not proportionately reduced. However, the earlier study included more severe cases of FAS. Cerebellum The cerebellum is composed of an outer layer of gray matter that covers a white core of connecting fibers and is attached to the brain stem at the level of the pons. It is indirectly involved in regulating movement, balance, and posture (Ghez, 1991). Numerous FAS autopsy studies reported cases with abnormalities of the cerebellum ranging from cerebellar dysgenesis (Clarren et al., 1978; Coulter et al., 1993; Jones & Smith, 1973; Peiffer et al., 1979; Wisniewski et al., 1983) and the presence of cerebellar heterotopic cell clusters (Clarren et al., 1978; Peiffer et al., 1979), to hypoplasia (Wisniewski et al., 1983) or agenesis of the cerebellar vermis (Peiffer et al., 1979). Results from our MRI studies suggest that the cerebellum is also particularly sensitive to alcohol’s teratogenic effects. We reported reductions in the cerebellar vault in children with FAS (Mattson et al., 1992) and in children with PEA (Mattson et al., 1994). Our
Prenatal Exposure to Alcohol 5 more recent MRI study, specifically examining the effects of alcohol on the cerebellar vermis, revealed that the area of the anterior regions (lobules I to V) was reduced but the posterior and remaining regions were not (Sowell et al., 1996). Previous findings from an animal model similarly found abnormal development of the anterior region with apparent sparing of the posterior vermis in rats exposed prenatally to alcohol (Goodlett, Marcussen, & West, 1990).
NEUROPSYCHOLOGICAL FINDINGS Prenatal alcohol exposure has long been associated with subsequent cognitive and behavioral changes. In fact, FAS is reported to be among the leading known causes of mental retardation in the Western world (Abel & Sokol, 1987). Whether prenatal alcohol exposure produces a global deficit in intellectual functioning or whether individuals with such histories show a specific cognitive and/or behavioral profile of spared skills and weaknesses is still unresolved and under study. Furthermore, there is a tremendous need for additional research examining threshold effects for such cognitive and behavioral impairments (Jacobson & Jacobson, 1994) and the extent to which persons with PEA exhibit cognitive impairments similar to those seen in FAS. In an attempt to answer these questions, studies from our lab examined behavioral and cognitive abilities in children with the formal diagnosis of FAS and in children known to have heavy prenatal exposure to alcohol (PEA), but who lack the physical features of FAS. These children were typically referred for evaluation for FAS, but were found to be structurally normal and neither microcephalic nor growth retarded. Following is a review of our recent findings that illustrates some of the affected behavioral and cognitive domains in alcohol-exposed children. Intellectual Functioning Because alcohol’s effects on cognitive functioning might be considered one of its most devastating consequences, it is important to estimate the cognitive potential of alcoholexposed children. There have been numerous studies of cognitive ability in children with FAS, including both individual case reports and group studies. These studies typically report IQs ranging from Intellectually Deficient to Average, with these measures of IQ appearing to be relatively stable over time (Streissguth, Herman, & Smith, 1978). For a review of studies assessing the intellectual functioning in alcohol-exposed children, the reader is referred to Mattson and Riley (1998). A recent study from our laboratory using the Wechsler intelligence scales (Wechsler, 1974; Wechsler, 1989) to examine the intellectual functioning of children prenatally exposed to alcohol found that when compared to a normal control group matched for age, gender, and ethnicity, both the FAS and PEA groups showed deficits in overall IQ and on most subtest scores (Mattson, Riley, Gramling, Delis, & Jones, 1997). Overall, the PEA group’s scores were marginally higher than the FAS group’s, but few significant differences were found between the two alcohol-exposed groups on the individual subtests. These results demonstrate that high levels of prenatal alcohol exposure can lead to impairments in overall intellectual functioning. Furthermore, although these data do
6 Alcohol and Alcoholism not aid in the establishment of a threshold for alcohol-related effects, it is important to note that intellectual deficits can occur in children who do not meet the full criteria for FAS. Language Because children with FAS are often sociable, friendly, and outgoing, and appear younger than their chronological age, their language abilities may seem unimpaired. However, previous research showed that these children tend to have lower verbal abilities than non-exposed children (Abel, 1990; Abkarian, 1992; Conry, 1990). Recent findings from our lab found that children with FAS performed significantly lower than control children did on measures of word comprehension and naming ability, as measured by the Peabody Picture Vocabulary Test-Revised and the Boston Naming Test, respectively (Mattson, Riley, Gramling, Delis, & Jones, 1998). Similarly, children with PEA were found to have poor performances on these tests in comparison to the normal controls. Although the PEA children tended to have higher scores than the FAS children, these differences were not statistically significant. Thus, these findings are similar to those found for intellectual functioning and indicate that children exposed to alcohol without overt physical effects may nevertheless suffer from impairments in language functioning. Verbal Learning and Memory A recent study from our lab demonstrated deficits in verbal learning and memory in children with FAS when compared to nonexposed controls matched for age, gender, and ethnicity (Mattson, Riley, Delis, Stern, & Jones, 1996). Children were administered the California Verbal Learning Test-Children’s Version (CVLT-C), a learning task that assesses immediate and delayed recall and recognition memory for a word list. Children with FAS learned fewer words over five acquisition trials and subsequently had difficulty remembering words after a delay period of 20 minutes. These children also had increased numbers of intrusion and perseverative errors. That is, they tended to respond with words not on the original target list and also to repeat words already said. They were also less accurate in distinguishing target words from distracter words on a test of recognition memory and tended to make an increased number of false-positive errors. These results suggest that children with FAS failed to benefit from repeated exposure to the material. Whereas children in the control group improved their ability to remember the words across five trials, children in the FAS group seemed to show improvement only between the first two trials with little new learning on trials 3 through 5. However, although the FAS group tended to recall fewer words on the recall trials, there were no group differences on a retention measure for previously learned words. That is, although children with FAS initially recalled fewer words than did controls, they exhibited normal forgetting rates and were able to remember what they learned as well as controls did. These findings suggest that the memory impairment in the FAS group may be at the encoding level rather than at the retrieval level. Additionally, when compared to a control group matched for mental age (MA), children with FAS were similar to controls on learning and free recall measures, but were less able to discriminate the target words from distracters, made more false-positive
Prenatal Exposure to Alcohol 7 errors, and made more perseverative errors. In summary, there were few differences between the FAS and MA matched groups, suggesting that learning and memory deficits are related in part to an overall global intellectual deficit. However, the pattern of deficits that continued to exist when MA was controlled suggests that children with FAS may have specific problems with encoding and response inhibition that are unique to the disorder. Children with PEA also display impaired performance on the CVLT-C (Mattson, Riley, Gramling, et al., 1998). When compared to normal controls, group differences were found in learning and recall errors, but not on retention of learned information. Importantly, the FAS and PEA groups showed a similar pattern of impaired learning, and both demonstrated average retention of verbal material. Both alcohol-exposed groups made increased numbers of intrusion errors and had difficulty distinguishing target words from distracter words, but only the FAS group made more perseverative errors on recall and more false-positive errors on recognition testing. These results indicate qualitatively similar patterns of deficits in verbal learning and memory between the FAS and PEA children. Academic Skills Given their deficits in learning and overall intellectual ability, one might predict that children prenatally exposed to alcohol would also display impairments in academic skills. Previous studies showed decreased academic achievement and increased rates of learning problems in children exposed to alcohol prenatally (Streissguth, Barr, & Sampson, 1990). We (Mattson, Riley, Gramling, et al., 1998) recently examined the performances of children with FAS and PEA on the Wide Range Achievement Test-Revised (WRAT-R), a screening measure designed to assess academic skills, including reading, spelling, and arithmetic. Findings revealed that in all three academic areas, both groups of alcoholexposed children (FAS and PEA) had significantly lower scores than control children. These results suggest that children with PEA may suffer from similar academic problems to those faced by children with FAS. From a practical point of view, it must be stressed that although children with PEA may suffer many of the same academic difficulties as children with FAS, in fact, they may be less likely to receive the same type of remediation because educators may not realize that these difficulties are related to prenatal alcohol exposure. Fine-Motor Skills Previous studies showed that prenatal alcohol exposure affects the developing motor system (Marcus, 1987). Children of alcoholic mothers were described as having poor motor development, fine-motor dysfunction, and delayed gross-motor performance (Jones, Smith, Ulleland, & Streissguth, 1973). Studies reported deficits in fine- and gross-motor skills along with inferior coordination in children exposed to alcohol prenatally (Barr, Streissguth, Darby, & Sampson, 1990; Kyllerman et al., 1985). Animal studies also described motor dysfunctions such as gait disturbance (Hannigan & Riley, 1989) and poor balance (Meyer, Kotch, & Riley, 1990). Recently, fine-motor speed and coordination was assessed in children with FAS and PEA using the Grooved Pegboard.
8 Alcohol and Alcoholism Results revealed that both alcohol-exposed groups showed impaired performance on this test when compared to nonexposed controls (Mattson, Riley, Gramling, et al., 1998). These results, combined with past research, suggest that motor development might be sensitive to the effects of prenatal alcohol exposure. Visuospatial Abilities Visuospatial deficits in children with FAS were also reported, although relatively few studies examined this area. The few previous studies showed that children with FAS show deficits in visual-motor integration (Conry, 1990; Janzen, Nanson, & Block, 1995; Uecker & Nadel, 1996). We recently tested visual-motor integration skills in children with FAS and PEA using the Beery Developmental Test of Visual-Motor Integration (VMI). Both alcohol-exposed groups displayed poorer performance than did normal controls (Mattson, Riley, Gramling, et al., 1998). Again, these results indicate that children with PEA show patterns more similar to children with FAS than to normal control children. In another study examining specific visuospatial abilities, we found that children with FAS displayed deficits in the processing of hierarchical stimuli (Mattson, Gramling, Delis, Jones, & Riley, 1996). Visuospatial abilities were assessed using the global-local test, in which a large stimulus (the global feature) composed of smaller stimuli (the local features) is presented to the child. The alcohol-exposed children had difficulty recalling the local features of the stimulus, but showed no deficits in recalling the global or configural features of the stimulus. These deficits in local processing were found to be distinct from memory impairments because the same performance pattern was found when children were asked to copy the hierarchical stimuli. Therefore, the results suggest a specific impairment in processing of local features of hierarchical visual stimuli. Nonverbal Problem Solving Like visuospatial abilities, the problem-solving skills of alcohol-exposed children have received little attention. There is some evidence that children prenatally exposed to alcohol have difficulty planning and tend to perseverate on incorrect strategies when approaching problem-solving tasks (Kodituwakku et al., 1992). Recently we examined the performance of alcohol-exposed children on a test of nonverbal problem solving. A combined group of children with FAS and PEA was administered the Wisconsin Card Sorting Test (WCST), which requires nonverbal problem solving and cognitive flexibility. Previous research using this task with alcohol-exposed children, although limited, demonstrated that children exposed to alcohol prenatally display decreased accuracy (Carmichael Olson, Feldman, Streissguth, & Gonzalez, 1992), achieve fewer categories, and make more perseverative errors (Kodituwakku et al., 1992) than do normal controls. Findings from our data reveal that although alcohol-exposed children performed more poorly than normal controls on the WCST, their performance was better than expected based on their overall level of cognitive ability (Mattson, Roebuck, & Riley, 1996). These findings support the suggestion that alcohol exposure does not produce a unitary decline in functioning but, instead, some processes may be more affected than others.
Prenatal Exposure to Alcohol 9 SUMMARY AND CONCLUSIONS Our findings using MRI techniques revealed that children with FAS have specific volumetric reductions in their overall brain size, cerebellum, basal ganglia, diencephalon, and corpus callosum. When overall brain size is taken into account and results from a sample of PEA children are included in the analyses, the basal ganglia and specifically the caudate, the anterior vermis of the cerebellum, and specific areas of the corpus callosum all appear to be disproportionately affected by gestational alcohol exposure. These findings provide some of the first evidence that prenatal alcohol exposure produces a specific pattern of structural anomalies in the human brain. Our current studies examining the cognitive profile of children with FAS documented impairment in overall intellectual functioning as well as a pattern of relative weaknesses and spared skills in some distinct areas. Specifically, children with FAS show deficits in verbal learning, although verbal retention appears to be less affected. Children with FAS show deficits in processing hierarchical stimuli and exhibit specific weaknesses in the processing of local versus global features. Although it appears that nonverbal problemsolving skills are impaired when compared to normal controls, their performance is actually better than expected based on their overall level of intellectual functioning. These findings suggest that children with FAS exhibit overall deficits in cognitive functioning as assessed by standardized IQ tests, although further neuropsychological testing reveals a cognitive profile consisting of specific strengths and weaknesses. Therefore, although the reported cognitive deficits in alcohol-exposed children may reflect a general decline in overall intellectual ability, they do not correspond to an overall unitary decline in neuropsychological functioning. Much is known about the cognitive and behavioral abilities of children with FAS, although less is known about these abilities in children with PEA. Current findings suggest that the cognitive abilities of children with PEA are qualitatively similar to those of FAS children, although they show a tendency to be somewhat less impaired. It should be noted, however, that our results might be biased by the fact that some of the PEA children were ascertained retrospectively and may have been referred because of behavioral problems. However, the majority of our PEA subjects were identified prospectively or in the newborn period, before any behavioral or cognitive problems developed. We noted no systematic difference as a result of these different ascertainment procedures. Most importantly, our results indicate that, at the very least, a subset of children with PEA may suffer from effects of prenatal alcohol exposure even though overt physical signs are absent. This chapter provides an overview of recent work assessing alcohol’s effects on the developing brain in humans and the resulting behavioral and cognitive impairments that may ensue. Numerous studies showed cognitive and behavioral impairments in children diagnosed with FAS. However, it is not yet clear how brain malformations are related to cognitive functioning. Understanding the specific effects of alcohol on the developing brain may provide insight into the cause and nature of these cognitive and behavioral deficits. Given that there is still much to learn about these brain anomalies, corresponding deficits in brain functioning are under study.
10 Alcohol and Alcoholism ACKNOWLEDGMENTS This manuscript was supported in part by the National Institute on Alcohol Abuse and Alcoholism Grant No. AA10417 to E.P.Riley.
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Prenatal Exposure to Alcohol 11 Goodlett, C.R., Marcussen, B.L., & West, J.R. (1990). A single day of alcohol exposure during the brain growth spurt induces brain weight restriction and cerebellar Purkinje cell loss. Alcohol, 7, 107–114. Hannigan, J.H., & Riley, E.P. (1989). Prenatal ethanol alters gait in rats. Alcohol, 5, 451–454. Hynd, G.W., Semrud-Clikeman, M., Lorys, A.R., Novey, E.S., Eliopulos, D., & Lyytinen, H. (1991). Corpus callosum morphology in attention deficit-hyperactivity disorder: Morphometric analysis of MRI. Journal of Learning Disabilities, 24(3), 141–146. Jacobson, J.L., & Jacobson, S.W. (1994). Prenatal alcohol exposure and neurobehavioral development: Where is the threshold? Alcohol Health & Research World, 18, 30–36. Janzen, L.A., Nanson, J.L., & Block, G.W. (1995). Neuropsychological evaluation of preschoolers with fetal alcohol syndrome. Neurotoxicology and Teratology, 17(3), 273–279. Jeret, J.S., & Serur, D. (1991). Fetal alcohol syndrome in adolescents and adults [Letter to the editor]. Journal of the American Medical Association, 266(8), 1077. Jeret, J.S., Serur, D., Wisniewski, K., & Fisch, C. (1986). Frequency of agenesis of the corpus callosum in the developmentally disabled population as determined by computerized tomography. Pediatric Neuroscience, 12, 101–103. Jeret, J.S., Serur, D., Wisniewski, K.E., & Lubin, R.A. (1987). Clinicopathological findings associated with agenesis of the corpus callosum. Brain Development, 9, 225–264. Johnson, V.P., Swayze II, V.W., Sato, Y., & Andreasen, N.C. (1996). Fetal Alcohol Syndrome: Craniofacial and central nervous system manifestations. American Journal of Medical Genetics, 61, 329–339. Jones, K.L., & Smith, D.W. (1973). Recognition of the fetal alcohol syndrome in early infancy. Lancet, 2, 999–1001. Jones, K.L., Smith, D.W., Ulleland, C.N., & Streissguth, A.P. (1973). Pattern of malformation in offspring of chronic alcoholic mothers. Lancet, 1, 1267–1271. Kinney, H., Faix, R., & Brazy, J. (1980). The fetal alcohol syndrome and neuroblastoma. Pediatrics, 66(1), 130–132. Kodituwakku, P.W., Handmaker, N.S., Cutler, S.K., Weathersby, E.K., Handmaker, S.D., & Aase, J.M. (1992). Specific impairment of self regulation in FAS/FAE: A pilot study. Alcoholism: Clinical and Experimental Research, 16(2), 381. Kolb, B., & Whishaw, I.Q. (1990). Fundamentals of human neuropsychology. (3rd ed.). New York: W.H.Freeman. Kyllerman, M., Aronson, M., Sabel, K.-G., Karlberg, E., Sandin, B., & Olegard, R. (1985). Children of alcoholic mothers: Growth and motor performance compared to matched controls. Acta Paediactrica Scandinavica, 74, 20–26. Marcus, J.C. (1987). Neurological findings in the fetal alcohol syndrome. Neuropediatrics, 18(3), 158–160. Mattson, S.N., Gramling, L., Delis, D.C., Jones, K.L., & Riley, E.P. (1996). Global-local processing in children prenatally exposed to alcohol. Child Neuropsychology, 2(3), 165–175. Mattson, S.N., & Riley, E.P. (1996). Brain anomalies in fetal alcohol syndrome. In E. L.Abel (Ed.), Fetal alcohol syndrome: From mechanism to prevention (pp. 51–68). New York: CRC Press.
12 Alcohol and Alcoholism Mattson, S.N., & Riley, E.P. (1998). A review of the neurobehavioral deficits in children with fetal alcohol syndrome or prenatal exposure to alcohol. Alcoholism: Clinical and Experimental Research, 22(2), 279–294. Mattson, S.N., Riley, E.P., Delis, D.C., Stern, C., & Jones, K.L. (1996). Verbal learning and memory in children with fetal alcohol syndrome. Alcoholism: Clinical and Experimental Research, 20(5), 810–816. Mattson, S.N., Riley, E.P., Gramling, L., Delis, D.C., & Jones, K.L. (1997). Heavy prenatal alcohol exposure with or without physical features of the fetal alcohol syndrome leads to IQ deficits. Journal of Pediatrics, 131(5), 718–721. Mattson, S.N., Riley, E.P., Gramling, L., Delis, D.C., & Jones, K.L. (1998). A neuropsychological comparison of alcohol-exposed children with or without physical features of the fetal alcohol syndrome. Neuropsychology, 12(1), 146–153. Mattson, S.N., Riley, E.P., Jernigan, T.L., Ehlers, C.L., Delis, D.C., Jones, K.L., Stern, C., Johnson, K.A., Hesselink, J.R., & Bellugi, U. (1992). Fetal alcohol syndrome: A case report of neuropsychological, MRI, and EEG assessment of two children. Alcoholism: Clinical and Experimental Research, 16(5), 1001–1003. Mattson, S.K., Riley, E.P., Jernigan, T.L., Garcia, A., Kaneko, W.M., Ehlers, C.L., & Jones, K.L. (1994). A decrease in the size of the basal ganglia following prenatal alcohol exposure: A preliminary report. Neurotoxicology and Teratology, 16(3), 283–289. Mattson, S.N., Riley, E.P., Sowell, E.R., Jernigan, T.L., Sobel, D.R., & Jones, K.L. (1996). A decrease in the size of the basal ganglia in children with fetal alcohol syndrome. Alcoholism: Clinical and Experimental Research, 20, 1088–1093. Mattson, S.N., Roebuck, T.M., & Riley, E.P. (1996). Wisconsin card sorting performance in children prenatally exposed to alcohol [Abstract]. Alcoholism: Clinical and Experimental Research, 20, 74A. Meyer, L.S., Kotch, L.E., & Riley, E.P. (1990). Alterations in gait following ethanol exposure during the brain growth spurt in rats. Alcoholism: Clinical and Experimental Research, 14(1), 23–27. Miller, M.W. (Ed.). (1992). Development of the Central Nervous System: Effects of Alcohol and Opiates. New York:Wiley-Liss. Peiffer, J., Majewski, R., Fischbach, H., Bierich, J.R., & Volk, B. (1979). Alcohol embryoand fetopathy. Journal of the Neurological Sciences, 41, 125–137. Riley, E.P., Mattson, S.N., Sowell, E.R., Jernigan, T.L., Sobel, D.R., & Jones, K.L. (1995). Abnormalities of the corpus callosum in children prenatally exposed to alcohol. Alcoholism: Clinical and Experimental Research, 19(5), 1198–1202. Ronen, G.M., & Andrews, W.L. (1991). Holoprosencephaly as a possible embryonic alcohol effect. American Journal of Medical Genetics, 40, 151–154. Sowell, E.R., Jernigan, T.L., Mattson, S.N., Riley, E.P., Sobel, D.R., & Jones, K.L. (1996). Abnormal development of the cerebellar vermis in children prenatally exposed to alcohol: Size reduction in lobules I through V. Alcoholism: Clinical and Experimental Research, 20(1), 31–34. Streissguth, A.P., Barr, H.M., & Sampson, P.D. (1990). Moderate prenatal alcohol exposure: Effects on child IQ and learning problems at age 7 1/2 years. Alcoholism: Clinical and Experimental Research, 14(5), 662–669.
Prenatal Exposure to Alcohol 13 Streissguth, A.P., Herman, C.S., & Smith, D.W. (1978). Stability of intelligence in the fetal alcohol syndrome: A preliminary report. Alcoholism: Clinical and Experimental Research, 17, 80, 252 Uecker, A., & Nadel, L. (1996). Spatial locations gone awry: Object and spatial memory deficits in children with fetal alcohol syndrome. Neuropsychologia, 34, 209–233. Wechsler, D. (1974). Manual for the Wechsler Intelligence Scale for Children—Revised. San Antonio: Psychological Corporation. Wechsler, D. (1989). Manual for the Wechsler Preschool and Primary Scale of Intelligence—Revised. San Antonio: Psychological Corporation. Wisniewski, K., Dambska, M., Sher, J.H., & Qazi, Q. (1983). A clinical neuropathological study of the fetal alcohol syndrome. Neuropediatrics, 14, 197–201.
2 Alcohol-Induced Brain Damage During Development: Potential Risk Factors Wei-Jung A.Chen James R.West Texas A&M University
More than 2 decades ago, two groups of clinicians, one in France (Lemoine, Harrousseau, Borteyru, & Menuet, 1968) and one in the United States (Jones, Smith, Ulleland, & Streissguth, 1973), independently reported birth defects resulting from alcohol consumption during pregnancy. Although the French report was published first, the medical community did not recognize the seriousness of alcohol-induced birth defects until 5 years later when Jones and Smith (1973) introduced the term fetal alcohol syndrome (FAS) to describe the specific constellation of abnormalities found in some offspring born to alcoholic mothers. The characteristic features of FAS include (a) facial dysmorphology, including features such as flattened philtrum (the midline groove area between base of the nose and upper lip), thin upper lip, and flat midface; (b) prenatal and postnatal growth retardation, including significantly lower birth weight; and (c) central nervous system (CNS) dysfunction, from hyperactivity to attention deficits and learning disabilities. These distinctive features are the current diagnostic criteria for FAS. Recently, the Institute of Medicine report on FAS proposed a modified list of diagnostic criteria (Stratton, Howe, & Battaglia, 1996), adding the history of maternal drinking, either confirmed or unconfirmed, as another major criterion. Stratton et al. (1996) also proposed criteria for diagnoses of partial FAS with a confirmed maternal alcohol drinking history. Alcohol-related birth defects (ARBDs) and alcohol-related neurodevelopmental disorders (ARNDs) were also included to account for those children who were born with abnormalities that did not meet all three principal characteristic features of FAS. The ARND category may correspond to the PEA (i.e., prenatal exposure to alcohol) group described by Roebuck, Mattson, and Riley (chapter 1, this volume). It is critical to develop these criteria so that affected individuals can be diagnosed consistently and the appropriate medical treatments and psychological evaluations can be implemented.
INCIDENCE OF FAS: THE ALARMING FACTS A recent report from Abel (1995) indicated that the incidence of FAS is estimated at 0.97 cases per 1,000 live births worldwide, almost a three-fold increase compared with a 1987 estimate of 0.33 cases per 1,000 live births in the Western world (Abel & Sokol, 1987). The most startling result from this recent survey is that the estimate of the FAS incidence within the United States (1.97 cases per 1,000 live births) was double that of the worldwide estimate. It is believed that the frequencies of the babies born with partial FAS, ARBDs, and ARNDs are much higher. Collectively, these findings indicated clearly that alcohol abuse among women of childbearing age remains a major health concern in our society.
Alcohol-Induced Brain Damage During Development 15
EVIDENCE OF ALCOHOL-INDUCED BRAIN DEFICITS: PROGRESS IN THE PAST In the past 20 years, neuroscientists in both clinical and experimental settings made substantial progress in understanding the wide spectrum of alcohol-induced brain deficits. For example, the most recent clinical evidence regarding alcohol-induced neuroanatomical damage comes from research using the noninvasive technique magnetic resonance imaging (MRI; see chapter 1). Riley and his colleagues demonstrated that children with FAS showed a thinned corpus callosum and size reductions in the anterior cerebellum and the basal ganglia (Mattson, Jernigan, & Riley, 1994; Mattson et al., 1996; Sowell et al., 1996). Using animal model systems, experimental research allows a more detailed examination of alcohol-induced brain injuries from a microscopic approach in a controllable laboratory environment. For instance, our laboratory has published numerous reports documenting that alcohol exposure during the brain growth spurt, a dynamic period of brain growth, resulted in the loss of Purkinje and granule cells in the cerebellum (Hamre & West, 1993; Pierce, Goodlett, & West, 1989), mitral and granule cells in olfactory bulb (Bonthius, Bonthius, Napper, & West, 1992), and pyramidal cells in the hippocampus (Bonthius & West, 1990; Pierce, Goodlett, & West, 1989). In addition to the detrimental effects of alcohol on neuroanatomical assessments, alcohol exposure during gestation (in utero) or in the early postnatal period (brain growth spurt) in the rat significantly affects the development of several neurochemical systems. More recently, Maier, Chen, and West (1996) reported that binge-like alcohol exposure from embryonic day (E) 1 to E20 significantly altered the fetal neurotransmitter profiles assessed on E20 in a rat model system. Furthermore, this in utero alcohol exposure regimen markedly affected the responsiveness of the developing dopaminergic system to an acute cocaine challenge during the early postnatal stage (Chen, Maier, & West, 1997). Together, these empirical findings demonstrated clearly that in utero or early postnatal alcohol exposure severely damages and impedes the normal development of the central nervous system.
KEY UNANSWERED QUESTIONS: DIRECTIONS FOR FUTURE RESEARCH The following discussion focuses on factors that may influence the outcome of alcohol exposure on the developing brain. Generally, these potential risk factors exacerbate the deleterious effects of alcohol. It is potentially important to identify such factors not only to minimize their interaction with alcohol, so that any alcohol-induced harmful consequences on the developing fetus can be lessened, but also to account for several pressing unanswered questions. For example, why do some women who abuse alcohol during pregnancy deliver babies without FAS or serious ARBDs? What is the threshold for alcohol consumption to induce fetal brain damage? Is there any developmental stage of fetal brain growth that is particularly vulnerable to alcohol insult? In this chapter, efforts focus on providing information that may eventually help to answer some of the
16 Alcohol and Alcoholism
current questions. Much of the evidence used to address these issues is based on research using animal model systems. Like many other areas of clinical research, a major obstacle in making significant progress in clinical fetal alcohol research is the reliability of the self-reports from the interviews of women who abused alcohol during pregnancy. Such information is believed to be critical for clinicians to perform accurate diagnoses and to develop intervention strategies. The lack of reliability can be, in part, an intentional act due to guilt, or an unintentional response, such as loss of memory of the drinking history due to time, or other factors. Variations in blood alcohol concentrations (BACs) among women, or for the same woman across drinking episodes, cannot be assessed from self-report histories. For these reasons, it is difficult to establish accurate correlations between alcohol drinking histories and alcoholinduced detrimental outcomes on the developing fetus. Fortunately, using animal models provides controlled experimental manipulations and, therefore, the experimental results can be interpreted with fewer confounding influences. Prior to the detailed discussion of these risk factors, a brief introduction of the brain growth spurt and artificial rearing techniques is presented to facilitate the understanding of the studies discussed later in the chapter. Brain Growth Spurt The brain growth spurt is a period of rapid brain growth characterized by a dramatic increase in brain weight generally between postnatal days 4 to 9 in the rat (Dobbing & Sands, 1973, 1979). The neurodevelopmental events during the brain growth spurt include accelerated synaptogenesis and cerebellar granule cell proliferation. Brain development in this period is vulnerable to a variety of neuroteratogenic insults, including alcohol (Goodlett, Marcussen, & West, 1990; Hamre & West, 1993; Phillips & Krueger, 1990). Although the general stages of brain development are similar across mammalian species, the timing of the brain growth spurt relative to birth can be quite different. For example, in humans, the brain growth spurt begins late in the second trimester, peaks around birth, and continues into postnatal life. In contrast, the entire brain growth spurt in rats occurs postnatally. Therefore, comparisons among species regarding the issues of brain development must consider the timing of the brain growth spurt for each species. Some of the experimental research examining the neuroteratogenic effects of alcohol in rats involves administering the alcohol directly to the neonatal pups, usually from postnatal days 4 through 9. This early postnatal alcohol exposure regimen, or so-called “third trimester equivalent” exposure, mimics maternal drinking during the third trimester, a developmental stage that encompasses a key part of the brain growth spurt in humans, allowing for comparisons to the deleterious effects of alcohol exposure in humans during the third trimester. Artificial Rearing Techniques Artificial rearing (also known as “pup-in-the-cup”) of neonatal rat pups in the absence of their mother is widely used in studying the effects of neuroteratogens on the developing brain (West, 1993). A major advantage of artificial rearing techniques is limiting
Alcohol-Induced Brain Damage During Development 17 potentially confounding influences of teratogens on somatic growth by providing adequate nutrient intake. To maintain optimal somatic growth and eliminate the potential confounding effects of alcohol on suckling behavior (nutrient intake), artificial rearing is the technique of choice. The detailed information regarding artificial rearing procedures and the constituents of the diets (milk formula) are described in Diaz (1991) and West, Hamre, and Pierce (1984). Briefly, pups are surgically implanted with an intragastric cannula under anesthesia (e.g., methoxyflurane [Metofane®]), typically on postnatal day 4. Pups within a given litter are maintained in fur-lined plastic cups partially immersed in 37°C water in an enclosed aquarium. Daily nutritional requirements are delivered via formula-filled syringes in a timer-activated infusion pump. The pumps are activated every 2 hours and administer 1/12 of the daily volume of milk formula over each 20-minute infusion period. The volume of formula (in ml) given to the pups each day is calculated as 33% of the mean body weight (in grams) of the litter mates being reared. All pups are given 20-minute feedings, with a 100-min interval between feedings. Depending on the experimental design, alcohol or other drugs can be mixed with the formula in various concentrations and can be administered in one or more of the 12 daily feedings. In several published neuroanatomical and neurochemical reports, artificial rearing techniques do not produce significant deficits on dependent measures when compared with normal rearing conditions (pups reared by dams; Bonthius et al., 1992; Bonthius & West, 1990; Goodlett et al., 1990; Kelly, Black, & West, 1989; Napper & West, 1995). Not surprisingly, however, there is evidence indicating that some measures are more sensitive to the artificial rearing methods, and the effects observed following the experimental manipulations may be partially due to artificial rearing (Kelly, 1996; Kelly, Mahoney, Randich, & West, 1991). Therefore, it is necessary to rear both drug-exposed and control subjects in the same artificial rearing environment and to include normally reared suckle controls, to allow assessment of the effects of the abnormal developmental environment of artificial rearing. Overall, artificial rearing techniques offer several advantages compared with other methods in maintaining appropriate somatic growth following an early postnatal drug exposure (Chen, Andersen, & West, 1993, 1994b).
RISK FACTORS: FACTORS INFLUENCING THE SEVERITY OF ALCOHOL-INDUCED BRAIN DAMAGE There are at least four major risk factors that can interact with alcohol in influencing alcoholinduced brain damage: the peak blood alcohol concentration (BAC), the developmental timing of alcohol intake, genetic differences, and polydrug use. The majority of the findings cited in the following sections are derived from animal research where the experimental manipulations were conducted in an environment that minimized confounding influences. Blood Alcohol Concentration (BAC) Work from our laboratory demonstrated convincingly that the BAC is a reliable indicator or, and predictor of, alcohol-induced brain damage (for a review, see West, Goodlett, f Bonthius, Hamre, & Marcussen, 1990). Bonthius and West (1988) found that the magnitude of the brain growth restriction, or microencephaly (small brain for body size), as measured by reductions in brain weight, depends on the peak BAC. In Bonthius and West (1988), artificially reared pups were given one of seven alcohol doses (from 2.5 to
18 Alcohol and Alcoholism 7.5 g/kg/day) from postnatal days 4 through 9. The peak BAC achieved from these alcohol doses on postnatal day 6 ranged from 30 mg/dl to higher than 500 mg/dl. The correlation between the reductions in brain weight examined on postnatal day 10 and the peak BACs was !0.916. In addition, Goodlett and West (1992) reported that similar alcohol-induced reductions in brain weight persisted until postnatal day 260 (adulthood) and were highly correlated with the peak BACs measured on postnatal day 6 (neonatal period). Taken together, these findings suggest strongly that peak BAC is a reliable predictor of severity of alcohol-induced brain growth restrictions. Given that peak BAC is a key determinant for the severity of alcohol-induced brain damage, then factors or manipulations that affect peak BACs should affect the degree of brain injury. Alcohol Dose. Within an individual, consumption of larger amounts of alcohol over a given period of time results in higher blood alcohol concentrations. As indicated previously, Bonthius and West (1988) reported that mean BACs in rats increased proportionally as a function of increases in alcohol dose. In a recent study, Cudd, Chen, and West (1996) demonstrated dose-dependent increases in BACs after intravenous administration of alcohol in an ovine model. In general, BACs are closely related to the dose of alcohol for a given pattern of alcohol exposure. Pattern of Alcohol Exposure. The pattern of alcohol exposure can also be important in determining the neurotoxic effects of alcohol. Artificial rearing techniques allow comparisons among the effects of different patterns of alcohol exposure, such as bingelike drinking versus continuous alcohol exposure. Binge-drinking patterns are a common form of abuse in humans, and they appear to produce more injurious consequences than less condensed drinking patterns. Experimental findings demonstrated clearly that bingelike alcohol exposure leads to a higher BAC and subsequently results in more severe brain injury than continuous alcohol exposure when the total daily dose is the same. In Bonthius and West (1990), alcohol was given to artificially reared rat pups in one of three different feeding schedules: (a) 6.6 g/kg/day alcohol was divided evenly into 12 feedings (Schedule I); (b) 4.5 g/kg/day alcohol was given in four of the 12 daily feedings (Schedule II); (c) 4.5 g/ kg/day alcohol was administered in a condensed fashion in 2 of the 12 feedings (Schedule III). Following these alcohol exposure paradigms, the peak BACs attained from Schedule I, II, and III were approximately 50, 200, and 360 mg/dl, respectively. Even though the total amount of alcohol administered per day was greatest in the Schedule I group, the peak BACs were the smallest. Although the total daily dose was equal in the Schedule II and III groups, the peak BACs were highest in the more condensed Schedule III group. The effects of alcohol following these exposure regimens were assessed by measuring the density of profiles of hippocampal pyramidal cells and cerebellar Purkinje and granule cells in single 2 mm-thick sections. As hypothesized, density reductions in these neuronal populations were correlated with BACs, and there was a statistically significant decrease in the density of all three cell types after the Schedule III exposure (Fig. 2.1). Although Schedule I delivered the highest dose of alcohol (6.6 g/kg/day), it caused the least effect on neuronal densities. These findings suggest that the alcohol-induced brain restrictions and density reductions of hippocampal CA1 pyramidal, cerebellar Purkinje, and cerebellar granule cells are more dependent on peak BAC than on the total daily alcohol dose per se. The pattern of alcohol exposure markedly affects peak BACs and the degree of alcohol-induced brain damage.
Alcohol-Induced Brain Damage During Development 19 Alcohol Concentration. Alcohol concentration refers to the concentration of the alcohol solution, not to dose or BAC. For a given dose of alcohol, administering solutions with higher alcohol concentrations can result in lower BACs. Using an animal model system
FIG. 2.1.The effect of pattern of alcohol exposure on neuronal numbers. Artificially reared neonatal rat pups were exposed to alcohol following
three different exposure regimens from postnatal days 4 to 9. Schedule I group: 6.6 g/kg/day alcohol was divided evenly into 12 daily feedings; Schedule II group: 4.5 g/kg/ day alcohol was administered in four of the 12 daily feedings; Schedule III group: 4.5 g/kg/day alcolhol was given in a condensed fashion in two of the 12 daily feedings. Two control groups, suckle and gastrostomy controls, were also included. (A) The mean numbers of the pyramidal cells in hippocampal CA1 field as a function of various experimental treatments. The number of pyramidal cells was significantly reduced in Schedule III alcohol exposure group, but not in Schedules I & II, when compared with those of control groups. It is of interest to note that the numbers of pyramidal cells in hippocampal CA2/3 and 4 fields were not affected after alcohol treatment regardless of the pattern of exposure. (B & C) Similar to the hippocampal pyramidal cells, cerebellar Purkinje and granule cells were reduced as a consequence of alcohol exposure. However, the decreases of cerebellar Purkinje and granule cells were observed not only after the Schedule III alcohol exposure, but also the Schedule II. These findings suggest that cerebellar Purkinje and granule cells are more vulnerable to alcohol than hippocampal pyramidal cells, since the moderate level of peak BAC after Schedule II alcohol exposure was sufficient to deplete cerebellar Purkinje and granule cells, but not pyramidal cells. *indicates significantly different from suckle and gastrostomy controls, indicates significantly different from suckle control, gastrostomy control, and Schedule III group. #
indicates significantly different from all other four groups.
20 Alcohol and Alcoholism Maier, Strittmatter, Chen, and West (1995) examined this issue by giving 5 g/kg/day of alcohol in four different concentrations (15%, 22.5%, 30%, and 45% v/v) to adult, nonpregnant female rats once daily through intragastric intubation. Blood samples of each animal were collected seven times on the sampling day and 4 days within the 20-day test period. Intubation with the highest alcohol concentration (45%) produced the lowest peak BACs on all 4 sampling days. This finding is consistent with that of a previous report by Roine, Gentry, Lim, Baraona, and Lieber (1991) showing that intragastric administration of 1.0 g/kg alcohol solution to adult male rats in a concentration of 40% (w/v) produced a lower peak BAC and a small area under the blood alcohol curve (AUC) compared with 1.0 g/kg doses given in 4% or 16% solutions. In the same report, Roine et al. (1991) also examined the effects of alcohol concentration on human subjects. Interestingly, after a 0.3 g/kg alcohol dose, the peak BAC achieved after drinking a 40% alcohol solution was significantly lower than after consuming a 4% alcohol solution. These results suggest that alcohol concentration can influence the magnitude of the peak BAC and that after a certain point (as yet undetermined), higher concentrations actually produce lower peak BACs. Interaction With Other Agents. There are many agents that may interact with alcohol to produce higher BACs by interfering with the enzymatic metabolism of alcohol. The major pathway for alcohol metabolism is the conversion of alcohol to acetaldehyde by alcohol dehydrogenase (ADH); then acetaldehyde is further degraded to acetate and water by acetaldehyde dehydrogenase. Generally, blocking the ADH increases BACs. Chen, McAlhany, and West (1995) reported that intraperitoneal injections of 4-methylpyrazole (4-MP), an ADH inhibitor, prior to daily alcohol feedings on postnatal days 4 through 9, significantly increased peak BACs in artificially reared neonatal rats. Pups were exposed to a 3.3 g/kg/day alcohol dose with or without 50 mg/kg/day 4-MP, and the BACs were measured three times daily on postnatal days 6 and 8. Peak BACs for pups receiving the 3.3 g/kg alcohol alone were 200 mg/dl on both sampling days. However, the peak BACs for the pups also given 50 mg/kg 4-MP were almost doubled. The increase in peak BAC was in accord with the severity of the brain injury: there were significant reductions in forebrain, cerebellum, and brainstem weights in response to the higher BACs (Fig. 2.2). Similarly, in human studies there are reports of agents that may interfere with alcohol dehydrogenase activity and result in higher BACs. Caballeria, Baraona, Rodamilans, and Lieber (1989) reported that the over-the-counter heartburn medicine Tagamet® (cimetidine,
Alcohol-Induced Brain Damage During Development 21
FIG.2.2.The effects of alcohol and its interaction with 4methylpyrazole (4-MP, an alcohol dehydrogenase inhibitor) on brain weight to body weight ratios. Artificially reared neonatal rat pups were exposed to alcohol(3.3 g/kg/day in two of the 12 daily feedings), 4-MP (50 mg/kg/day; i.p. injection) or the combination of both. The mean forebrain, cerebellum, and brainstem weight to body weight ratios as a function of various experimental treatments were presented in (A), (B), and (C), respectively. The coadministration of alcohol and 4MP significantly reduced the brain to body weight ratios in all three regions assessed. These reductions in ratios were due to the higher BACs following the inhibition of alcohol dehydrogenase activity by 4-MP. Moreover, alcohol exposure alone decreased the mean brain to body weight ratio only in cerebellum, suggesting that cerebellum is more susceptible to alcohol than other brain regions. *indicates significantly different from gastrostomy, 0g EtOH/50mg 4-MP, and3.3g EtOH/0mg 4-MP groups. ¶ indicates significantly different from gastrostomy and 0g EtOH/50mg 4-MP groups. Note: Suckle controls were not included in the overall analyses. However, independent t-tests were conducted to compare the data between suckle and gastrostomy controls. an H2 receptor antagonist) inhibited the activity of gastric ADH and resulted in higher BACs. Hernández-Munõz et al. (1990) demonstrated farther that the combination of alcohol with Zantac® (ranitidine), but not with Pepcid® (famotidine), yielded a higher peak BAC compared with the administration of alcohol alone. Although there is no information available demonstrating that the interaction of alcohol with these nonprescription drugs worsens alcoholinduced brain injury in clinical settings, the findings from animal research may be extrapolated to human conditions to suggest that an increase in BAC in response to the interaction of alcohol and gastric ADH inhibitors could result in more severe damage to the developing brain.
22 Alcohol and Alcoholism
Temporal Vulnerability Within each species, the development of different neuronal populations in the brain takes place at different developmental periods according to sequences that are genetically regulated. For instance, in rats, the timing of neurogenesis for pyramidal cells in the hippocampus and for Purkinje cells in the cerebellum relative to birth is quite different, with the former occurring between gestational days 16 and 20, and the latter between gestational days 13 and 16 (Altman & Bayer, 1978; Bayer, 1980). The presence of alcohol at a specific time during brain development interacts with different brain regions or cell populations that are in different stages of development and, therefore, may have a differential impact on them. Clinically, it was suggested that alcohol exposure during the first trimester produces craniofacial anomalies compared with exposure during later trimesters. Day et al. (1989) reported that one drink (equivalent to one can of beer, 5 oz of wine, or 0.5 oz of absolute alcohol) per day for the first 2 months of pregnancy is sufficient to produce some facial dysmorphology. This is different from the characteristic facial hypoplasia, microcephaly (small head for body size), and growth retardation that is associated with alcohol exposure throughout gestation. Coles et al. (1991) reported that the reductions in head circumference were less severe if the mothers stopped drinking during the second trimester, compared with those who continued drinking. Similarly, Smith, Coles, Lancaster, Fernhoff, and Falek (1986) found that babies born to mothers who stopped drinking before the end of the second trimester had birth weights and head circumferences that were comparable to babies born to mothers who never drank during pregnancy. These findings suggest that the cessation of drinking during the course of pregnancy is beneficial to the developing fetus. It is difficult to determine whether a relationship exists between neurobehavioral or neuropathological outcomes and time of exposure in clinical studies. However, controlled animal experiments were conducted that have begun to identify the importance of the developmental timing of alcohol exposure on brain damage and behavior (see chapter 4, this volume, by Goodlett & Johnson). Marcussen, Goodlett, Mahoney, and West (1994) reported that effects on Purkinje cell density were more severe if the alcohol exposure occurred during Purkinje cell differentiation (postnatal), rather than during neurogenesis (prenatal). In that study, pups were exposed either prenatally to 5 g/kg/day of alcohol (from gestation days 13 to 18) via single daily intragastric intubations of their dams, or postnatally (from postnatal days 4 to 9) to single daily intubations of 2.5 g/kg/day of alcohol via artificial rearing. The mean peak BACs attained in the pregnant dams and postnatally exposed pups were 266 and 206 mg/dl, respectively. When cerebellar Purkinje cell densities were assessed on postnatal day 10, pups exposed postnatally, during the period of early differentiation for Purkinje cells, had significantly lower Purkinje cell densities than pups prenatally exposed to even higher BACs during the period of neurogenesis for Purkinje cells. Similarly, Phillips and Cragg (1982) reported that pups exposed to alcohol by vapor inhalation on postnatal days 3 and 4 exhibited more severe reductions in Purkinje cell density compared with those exposed to alcohol during the last 2 weeks of gestation (vapor inhalation to dams). These studies suggest that cerebellar Purkinje cells are more vulnerable to alcohol during differentiation than during neurogenesis.
Alcohol-Induced Brain Damage During Development 23 Temporal windows of vulnerability were identified in other neural structures as well. Phillips, Krueger, and Schubloom (1996) reported that time of exposure had a significant impact on alcohol-related effects on optic nerve development. With exposure on postnatal days 5 and 6, the number of glia cells and myelinated optic nerve fibers were reduced when compared with exposure on postnatal days 9 and 10. In the hippocampus, West and Hamre (1985) found that mossy fiber organization in the hippocampal formation was more severely altered after early postnatal alcohol exposure (during the third trimester equivalent in a rat model system) than following more prolonged prenatal alcohol exposure. Taken together, the findings discussed here support the hypothesis that the timing of the alcohol exposure (temporal vulnerability) is an influential factor in determining the severity of fetal alcohol-induced brain injury (West, 1987). Genetic Differences Identifying genetic differences as a major contribution to the variation in alcohol-induced deleterious effects during pregnancy in humans is not an easy task. Abel and Hannigan (1995) argued that the higher incidence of FAS seen among African Americans and Native Americans is not simply an issue of race. In their argument, they disputed the conjecture that race per se is an important determinant of the incidence of FAS. Rather, they suggested that socioeconomic status is an underlying factor that systematically varies with race to influence the incidence of FAS diagnoses. In any case, the consensus remains that no single race is immune to the problems of FAS. Although clinical findings regarding this genetic issue remain inconclusive, experimental research may shed light on the involvement of genetic factors that affect the magnitude of alcohol-induced brain damage.
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FIG. 2.3. Two selected lines of mice, long sleep (LS) and short sleep (SS), were exposed to 3.0 or 4.0 g/kg alcohol during gestation, and their adult offspring were assessed for brain growth restriction. This figure shows that the mean brain weight in the LS line was significantly decreased following 4.0 g/ kg alcohol when compared with control groups. However, no difference was found among four treatment groups in SS mice. These findings suggest that genetic factors play a role in affecting alcohol-induced brain growth restriction. Long-sleep (LS) and short-sleep (SS) mice were initially developed for the characteristic difference in the duration of the loss of righting reflex after alcohol administration. The LS line is more sensitive to the sedative-hypnotic effects of alcohol, exhibiting a longer duration of the loss of righting reflex. On the other hand, the SS line displays more resistance to those effects of alcohol. Goodlett, Gilliam, Nichols, and West (1989) demonstrated that the brains from adult offspring of LS dams intubated with alcohol during gestation were significantly smaller than those from the offspring of alcoholtreated SS dams (Fig. 2.3). The difference in brain growth restriction observed between LS and SS lines was not a function of BACs because the BACs for both lines ranged from 350 to 400 mg/dl during the period of alcohol treatment (gestation days 7 to 18). In addition to the selected lines, inbred strains are potentially useful tools to study issues related to genetic influences associated with FAS. Goodlett et al. (1989) and Maier, Mahoney, Goodlett, and West (1994) demonstrated that genetic variability plays a critical role in determining the degree of brain deficits following alcohol exposure in two different inbred rat strains, the Maudsley Reactive (MR) and the Marshall (M520). Using artificial rearing techniques, the pups of these two strains were exposed to 3.3, 4.4, or 5.5
Alcohol-Induced Brain Damage During Development 25 g/kg/day alcohol during the brain growth spurt and were assessed in terms of cerebellar weight and cerebellar Purkinje cell numbers. The cerebella of the MR strain had more severe reductions in weight than those of the M520 strain, even though the mean BAC in MRs was lower than that in M520s. Although both MR and M520 rats showed decreased total numbers of Purkinje cells, the reduction in Purkinje cells was more extensive in the MR than in the M520 strain. These findings support the hypothesis that genetic factors can influence the outcome of alcohol exposure on the developing brain and that mechanisms underlying these genetic-related influences may be independent from those associated with BACs. Polydrug Use Drug abuse continues to be a major concern in society, and the frequency of drug use is increasing. The most serious consequences of drug abuse, regardless of licit or illicit drugs, are thought to occur among women of childbearing age because the detrimental effects of drugs may affect not only those individuals who abuse the drugs, but also their developing fetuses. (American Public Health Association, 1993). Because alcohol may interact with some agents (e.g., 4-MP and cimetidine) to increase BACs, other drugs, that may not directly affect BACs, may nevertheless worsen the detrimental effects of alcohol. Recent efforts addressed this polydrug issue to broaden the knowledge of deleterious effects of alcohol and its interaction with other drugs on brain development. Concurrent use of alcohol and cocaine has been documented frequently in clinical studies. A recent report of 18 women who presented at delivery without prenatal care were randomly selected, interviewed, and tested for drug use. Astonishingly, half of them tested positive for both alcohol and cocaine use (DiGregorio, Barbieri, Ferko, & Ruch, 1993). Using the artificially reared animal model, Chen, Andersen, and West (1994a) reported that concomitant administration of alcohol and cocaine did not interact to restrict brain growth. Cocaine did not enhance alcohol-induced brain deficits, and cocaine itself did not exert any effects on brain growth restrictions or on Purkinje cell number (Chen, McAlhany, Maier, and West, 1996). Nevertheless, the concurrent use of alcohol and cocaine did produce a higher incidence of mortality than either drug alone, suggesting an additive or synergistic effect. Cocaine-induced mortality may be mediated through binding with the dopamine transporter (Hearn et al., 1991), but it is currently unknown whether this increase in mortality is mediated through neurotoxicity or cardiotoxicity. The increase in mortality may be an enhancing action of alcohol on cocaine-mediated mortality. Simultaneous exposure to alcohol and cocaine produces the neuropharmacologically active metabolite cocaethylene (Fig. 2.4; Jatlow et al., 1991). The reaction that produces cocaethylene is catalyzed by hepatic and possibly renal carboxylesterase via an ethyl transesterification (Boyer & Peterson, 1992; Dean, Christian, Sample, & Bosron, 1991). Direct administration of cocaethylene to neonatal pups during the brain growth period produced significant brain growth restrictions and alterations in the levels of neurotransmitters (Chen & West, 1997). Therefore, the formation of cocaethylene represents an additional risk factor for alcohol-induced brain deficits in the presence of cocaine. It is unclear why the combined exposure of alcohol and cocaine did not result in similar detrimental outcomes as those observed following cocaethylene exposure. One possible
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FIG. 2.4. The conversion of cocaine to cocaethylene at the presence of ethyl alcohol. explanation is that the doses of alcohol and cocaine used were not sufficient to produce the level of cocaethylene necessary to produce brain damage. The other possibility is that the enzymatic mechanism that converts cocaine to cocaethylene in the presence of alcohol is not fully developed among the neonates at the time of exposure. Alcohol and nicotine, two licit but addictive substances, are also likely to be abused together. There is a positive correlation between drinking and smoking (de Fiebre & Collins, 1992). Recently, Chen, Parnell, and West (1998) addressed this issue by exposing neonatal rats to alcohol and nicotine concurrently during the brain growth spurt. Similar to the findings from the alcohol and cocaine study, no additive or synergistic effects were found on brain growth restrictions or cerebellar Purkinje cell loss following the coadministration of alcohol and nicotine. However, contrary to the outcome after cocaine exposure, nicotine exposure alone severely restricted brain growth and depleted a significant number of vermal Purkinje cells. It is interesting to note that due to the pharmacokinetic interaction between alcohol and nicotine, the mean peak BAC was significantly reduced by nicotine. Although the loss of Purkinje cells resulting from alcohol exposure may be less severe as a consequence of this decrease in peak BAC, the overall brain damage from the coexposure of alcohol and nicotine may not be affected, since nicotine exposure alone produced a severe loss of Purkinje cells. This nicotine-induced loss of Purkinje cells could be sufficient to compensate for any positive effects on Purkinje cells that might be expected follow a decrease in peak BAC. Combined ingestion of aspirin and alcohol is common because aspirin can relieve some of the adverse consequences of heavy alcohol drinking. Animal studies indicate that this combination of alcohol and aspirin can result in more serious damage to the developing brain than alcohol alone in an animal model. Bonthius and West (1989) reported that a therapeutic dose of aspirin (50 mg/kg/day) given to neonatal rats during the brain growth spurt augmented alcoholinduced brain growth restriction. This action of aspirin in mediating brain injury was not related to BAC, since the peak BAC was not altered by the presence of aspirin. In contrast to aspirin’s exacerbation of alcohol-induced brain deficits during the brain growth spurt, the administration of aspirin prenatally was reported to protect against some alcohol-induced teratogenesis in mice (Randall, Anton, Becker, Hale, & Ekblad, 1991). The discrepancy between these two studies could be due to the differences in species, the timing of the coadministration of aspirin and alcohol (postnatal brain growth spurt in rats versus early gestation in mice) or the dependent measures (brain growth restriction versus limb and kidney defects). Regardless, the results from Bonthius and West (1989) suggest that the combination of alcohol and aspirin may exacerbate the damaging effects of alcohol on the developing brain.
Alcohol-Induced Brain Damage During Development 27 The findings from polydrug studies suggest that the effects of alcohol on neurodevelopment can be influenced by the presence of other drugs. Although no significant additive or synergistic actions on brain development are observed with the combination of alcohol and cocaine or nicotine, the interactive effects on mortality, the formation of cocaethylene and the neuroteratogenic effects of nicotine represent additional risks to the developing fetus beyond the intrinsic effects of alcohol.
CONCLUSION Since the goal of convincing women of reproductive age to refrain from drinking prior to and during pregnancy has not been successful, efforts to minimize the devastating effects of alcohol on a developing conceptus become more important. To help achieve this goal, a comprehensive understanding of alcohol’s detrimental effects and the underlying mechanisms responsible for these effects is required. Identifying the risk factors for alcohol-induced neurotoxicity is part of this effort and addresses some unanswered questions. In this chapter, four potential risk factors were reviewed that may be involved in the determination of the severity of alcohol-induced brain damage. Recognizing these risk factors provides a direction for studies focused on developing intervention strategies that could lessen the effects of alcohol on the developing brain, with the ultimate goal of decreasing the incidence of FAS.
ACKNOWLEDGMENTS This work was supported by Grant No. AA05523 from the National Institute on Alcohol Abuse and Alcoholism to James R.West. The authors thank Dr. Thomas H.Champney and Mr. Scott E.Parnell for their comments on the previous draft of this manuscript.
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28 Alcohol and Alcoholism Bonthius, D.J., Bonthius, N.E., Napper, R.M.A., & West, J.R. (1992). A stereological study of the effect of early postnatal alcohol exposure on the number of granule cells and mitral cells in the rat olfactory bulb. The Journal of Comparative Neurology, 324, 557–566. Bonthius, D.J., & West, J.R. (1988). Blood alcohol concentration and microencephaly: A dose-response study in the neonatal rat. Teratology, 37, 223–231. Bonthius, D.J., & West, J.R. (1989). Aspirin augments alcohol in restricting brain growth in the neonatal rat. Neurotoxicology and Teratology, 11, 135–143. Bonthius, D.J., & West, J.R. (1990). Alcohol-induced neuronal loss in developing rats: increased brain damage with binge exposure. Alcoholism: Clinical and Experimental Research, 14, 107–118. Boyer, C.S., & Peterson, D.R. (1992). Enzymatic basis for the transesterification of cocaine in the presence of ethanol: Evidence for the participation of microsomal carboxylesterases. The Journal of Pharmacology and Experimental Therapeutics, 260, 939–946. Caballeria, J., Baraona, E., Rodamilans, M., & Lieber, C.S. (1989). Effects of cimetidine on gastric alcohol dehydrogenase activity and blood ethanol levels. Gastroenterology, 96, 388–392. Chen, W.-J.A., Andersen, K.H., & West, J.R. (1993). Cocaine exposure during the brain growth spurt: Studies of neonatal survival, somatic growth, and brain development. Neurotoxicology and Teratology, 15, 267–273. Chen, W.-J.A., Andersen, K.H., & West, J.R. (1994a). Alcohol-induced brain growth restrictions (microencephaly) were not affected by concurrent exposure to cocaine during the brain growth spurt. Teratology, 50, 250–255. Chen, W.-J.A., Andersen, K.H., & West, J.R. (1994b). Cocaine-induced somatic growth deficit during the brain growth spurt is prevented by artificial-rearing. Neurotoxicology and Teratology, 16, 291–296. Chen, W.-J.A., Maier, S.E., & West, J.R. (1997). Prenatal alcohol treatment attenuated postnatal cocaine-induced elevation of dopamine concentration in nucleus accumbens: A preliminary study. Neurotoxicology and Teratology, 19, 39–46. Chen, W.-J.A., McAlhany, R.E., Jr., Maier, S.E., & West, J.R. (1996). Cocaine exposure during the brain growth spurt failed to produce cerebellar Purkinje cell loss in rat pups. Teratology, 53, 145–151. Chen, W.-J.A., McAlhany, R.E., Jr., & West, J.R. (1995). Alcohol dehydrogenase inhibitor, 4-methylpyrazole, augments ethanol-induced microencephaly in neonatal rats. Alcohol, 12, 351–355. Chen, W.-J.A., Parnell, S.E., & West, J.R. (1998). Neonatal alchol and nicotine exposure limits brain growth and depletes cerebellar Purkinje cells. Alcohol, 15, 33–41. Chen, W.-J.A., & West, J.R. (1997). Cocaethylene exposure during the brain growth spurt period: Brain growth restrictions and neurochemistry studies. Developmental Brain Research, 100, 220–229. Coles, C.D., Brown, R.T., Smith, I.E., Platzman, K.A., Erickson, S., & Falek, A. (1991). Effects of prenatal alcohol exposure at school age: I. Physical and cognitive development. Neurotoxicology and Teratology, 13, 1–11.
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30 Alcohol and Alcoholism Jones, K.L., & Smith, D.W. (1973). Recognition of the fetal alcohol syndrome in early infancy. Lancet, 2, 999–1001. Jones, K.L., Smith, D.W., Ulleland, C.N., & Streissguth, A.P. (1973). Pattern of malformation in offspring of chronic alcoholic mothers. Lancet, 1, 1267–1269. Kelly, S.J. (1996). Effects of alcohol exposure and artifical rearing during development on septal and hippocampal neurotransmitters in adult rats. Alcoholism:_Clinical and Experimental Research, 20, 670–676. Kelly, S.J., Black, A.C., & West, J.R. (1989). Changes in the muscarinic cholinergic receptors in the hippocampus of rats exposed to ethyl alcohol during the brain growth spurt. The Journal of Pharmacology and Experimental Therapeutics, 249, 798–804. Kelly, S.J., Mahoney, J.C., Randich, A., & West, J.R. (1991). Indices of stress in rats: Effects of sex, perinatal alcohol and artificial rearing. Physiology & Behavior, 49, 751–756. Lemoine, P., Harrousseau, H., Borteyru, J.P., & Menuet, J.C. (1968). Les enfants de parents alcooliques: anomalies obsrvées a propos de 127 cas [Children of alcoholic parents: Abnomalities observed in 127 cases]. L’Quest Medical, 25, 476–482. Maier, S.E., Chen, W.-J.A., & West, J.R. (1996). Prenatal binge-like alcohol exposure alters neurochemical profiles in fetal rat brain. Pharmacology, Biochemistry & Behavior, 4, 521–529. Maier, S.E., Mahoney, J.C., Goodlett, C.R., & West, J.R. (1994). Strain differences in susceptibility to alcohol-induced Purkinje cell loss demonstrated using unbiased stereological counting methods. Alcoholism: Clinical and Experimental Research, 18, 437. Maier, S.E., Strittmatter, M.A., Chen, W.-J.A., & West, J.R. (1995). Changes in blood alcohol levels as a function of alcohol concentration and repeated alcohol exposure in adults female rats: Potential risk factors for alcohol-induced fetal brain injury. Alcoholism: Clinical and Experimental Research, 19, 923–927. Marcussen, B.L., Goodlett, C.R., Mahoney, J.C., & West, J.R. (1994). Developing rat Purkinje cells are more vulnerable to alcohol-induced depletion during differentiation than during neurogenesis. Alcohol, 11, 147–156. Mattson, S.N., Jernigan, T.L., & Riley, E.P. (1994). MRI and prenatal alcohol exposure: Images provide insight into FAS. Alcohol Health & Research World, 18, 49–52. Mattson, S.N., Riley, E.P., Sowell, E.R., Jernigan, T.L., Sobel, D.R., & Jones, K.L. (1996). A decrease in the size of the basal ganglia in children with fetal alcohol syndrome. Alcoholism: Clinical and Experimental Research, 20, 1088–1093. Napper, R.M.A., & West, J.R. (1995). Permanent neuronal cell loss in the cerebellum of rats exposed to continuous low blood alcohol levels during the brain growth spurt: A stereological investigation. The Journal of Comparative Neurology, 362, 283–292. Phillips, S.C., & Cragg, B.G. (1982). A change in susceptibility of rat cerebellar Purkinje cells to damage by alcohol during fetal, neonatal and adult life. Neuropathology and Applied Neurobiology, 8, 441–454. Phillips, D.E., & Krueger, S.K. (1990). Effects of postnatal ethanol exposure on glial cell development in rat optic nerve. Experimental Neurology, 107, 97–105. Phillips, D.E., Krueger, S.K., & Schubloom, L.A. (1996) Effects of binge alcohol exposures at two different times on myelin development in rat optic nerve. Alcoholism: Clinical and Experimental Research, 20, 27A.
Alcohol-Induced Brain Damage During Development 31 Pierce, D.R., Goodlett, C.R., & West, J.R. (1989). Differential neuronal loss following early postnatal alcohol exposure. Teratology, 40, 113–126. Randall, C.L., Anton, R.R., Becker H.C., Hale, R.L., & Ekblad, U. (1991). Aspirin dosedependently reduces alcohol-induced birth defects and prostaglandin E levels in mice. Teratology, 44, 521–529. Roine, R.P., Gentry, R.T., Lim, R.T. Jr., Baraona, E., & Lieber, C.S. (1991). Effect of concentration of ingested ethanol on blood alcohol levels. Alcoholism: Clinical and Experimental Research, 15, 734–738. Smith, I.E., Coles, C.D., Lancaster, J., Fernhoff, P.M., & Falek, A. (1986). The effect of volume and duration of prenatal ethanol exposure on neonatal physical and behavioral development. Neurobehavioral Toxicology and Teratology, 8, 375–381. Sowell, E.R., Jernigan, T.L., Mattson, S.N., Riley, E.P., Sobel, D.R., & Jones, K.L. (1996). Abnormal development of the cerebellar vermis in children prenatally exposed to alcohol: Size reduction in lobules I through V. Alcoholism: Clinical and Experimental Research, 20, 31–34. Stratton, K., Howe, C., & Battaglia, R. (1996). (Eds.), Fetal Alcohol Syndrome: Diagnosis, Epidemiology, Prevention, and Treatment. Washington, DC: National Academic Press. West, J.R. (1993). Use of pup in the cup model to study brain development. Journal of Nutrition, 123, 382–386. West, J.R. (1987). Fetal alcohol-induced brain damage and the problem of temporal vulnerability: A review. Alcohol and Drug Research, 7, 423–441. West, J.R., Goodlett, C.R., Bonthius, D.J., Hamre, K.M., & Marcussen, B.L. (1990). Cell population depletion associated with fetal alcohol brain damage: Mechanisms of BACdependent cell loss. Alcoholism: Clinical and Experimental Research, 14, 813–818. West, J.R., & Hamre, K.M. (1985). Effects of alcohol exposure during different periods of development: Changes in hippocampal mossy fibers. Developmental Brain Research, 17, 280–284. West, J.R., Hamre, K.M., & Pierce, D.R. (1984). Delay in brain growth induced by alcohol in artificially reared rat pups. Alcohol, 1, 213–222.
3 Modification of Alcohol-Related Neurodevelopmental Disorders: In Vitro and In Vivo Studies of Neuroplasticity John H.Hannigan Dwight E.Saunders Loraine M.Treas Maureen A.Sperry Wayne State University
Fetal alcohol syndrome (FAS) was first defined in the early 1970s as a pattern of growth retardation, facial anomalies, and mental retardation in infants born to alcoholic women (Jones & Smith, 1973). Children with FAS show distinctive and persistent outcomes, including sometimes-subtle patterns of cognitive dysfunction (e.g., Jacobson & Jacobson, 1994; Roebuck, Mattson, & Riley, chapter 1, this volume; Streissguth et al., 1991; Streissguth et al., 1994). Researchers developed animal models to characterize the phenomenology, pathology, and risk factors associated with maternal alcohol consumption during pregnancy (Abel & Hannigan, 1995; Chen & West, chapter 2, this volume; Chernoff, 1997; Driscoll, Streissguth, & Riley, 1990). In vivo whole animal models of specific structural alcohol-related birth defects (ARBDs) and of the recently defined alcohol-related neurodevelopmental disorders (ARNDs; Stratton, Howe, & Battaglia, 1996) successfully met those goals (Randall, 1987; Schenker et al., 1990). The biological and neurobehavioral sequelae of prenatal alcohol exposure in animals can be remarkably consonant with the clinical and behavioral outcomes in humans (Abel, 1984; Driscoll et al., 1990; Roebuck et al., chapter 1, this volume). We recently reviewed the advantages and disadvantages of animal models in the study of ARNDs (Hannigan, 1996; Hannigan & Abel, 1996). In animals, many of the genetic, experiential, and sociobehavioral interactions operating potently to influence the intake and impact of alcohol in people can be controlled, excluded, and/or measured. For all these advantages, however, there are difficulties inherent to all animal models of fetal alcohol effects, a general term by which we mean any deleterious outcome including FAS, partial FAS, ARBDs, or ARNDs. There is no single “ideal” animal model of ARNDs, nor any model of FAS per se (Hannigan & Abel, 1996). Significant advances have been and will continue to be made using any of several well defined in vivo and in vitro models, each of which can approximate some of the key biological or behavioral features of alcohol teratogenesis or mimic specific ARBDs. All these models together have advanced our understanding of the biopsychological, cellular, and molecular causes and mechanisms of FAS and ARNDs (Abel & Hannigan, 1995). In this chapter, we describe how some of our research used whole animal models to assess potential treatments for fetal alcohol effects on behavior. We also present the results of studies with in vitro systems, models that we believe can advance our understanding of the neural sequelae of prenatal alcohol exposure. Our basic hypothesis is that prenatal alcohol-compromised behavior and cognition in FAS/ ARND may benefit from postnatal treatments that address those neural sequelae.
34 Alcohol and Alcoholism FETAL ALCOHOL EFFECTS IN RODENTS After prenatal alcohol exposure, rodents display age-dependent motor dysfunction (e.g., poor gait or hyperactivity) and learning deficits (cf. Meyer & Riley, 1986). Although many of the effects of fetal alcohol exposure, in children or rodents, can be long lasting (Bonthius & West, 1991; Streissguth et al., 1994), there are also reports that fetal alcohol effects are sometimes transient or “outgrown” (Hall, Church, & Berman, 1994; Riley, 1990; West & Goodlett, 1990). Spatial and temporal serial pattern learning, working memory, and spatial learning deficits were reported in both younger and older rats (e.g., Greene, Diaz-Granados, & Amsel, 1992; LaFiette, Carlos, & Riley, 1994), and older rats apparently remembered prior experience in a maze, showing no deficits in relearning (Hall et al., 1994). Even a single in utero episode of high peak maternal blood alcohol concentrations (BACs) in mice was able to produce a profound deficit in memory retrieval in 2-year-old mice, a deficit that was not evident in 3-month-old offspring (Dumas & Rabe, 1994). Despite some evidence of transient deficits in younger offspring (Melcer, Gonzalez, Barron, & Riley, 1994; Melcer, Gonzalez, & Riley, 1995; Riley, Barron, Melcer, & Gonzalez, 1993), these results suggest long-lasting ARNDs in rodents (cf. Becker, Randall, Salo, Saulnier, & Weathersby, 1994; Riley, 1990). The variable age-dependency and the nature of these behavioral and cognitive dysfunctions in rats and mice illustrate two features of fetal alcohol effects. First, these effects are modifiable, implying that some fetal alcohol effects may respond to treatment. Second, the nature of the CNS dysfunctions is expressed generally as a reduced capacity for basic adaptive functioning, including impaired neural or synaptic plasticity, poor learning, and/or abnormal responses to challenging situations. It appeared to us that by addressing the admittedly very general question of how alcohol compromises neural or neurobehaviorally plasticity, we may be able to facilitate recovery or ameliorate ARNDs.
TREATMENT OF FETAL ALCOHOL EFFECTS IN RODENTS Psychopharmacology We recently reviewed literature describing prenatal alcohol-induced shifts in behavioral response to psychoactive drugs (Hannigan & Randall, 1996). In addition to suggesting underlying neurochemical pathology, shifts in dose responses to psychoactive drugs in animals exposed prenatally to alcohol may indicate potential pharmacotherapies for FAS (cf. Hannigan & Blanchard, 1988). Prenatal alcohol-induced dose-response shifts appear to be most consistent following challenges with dopaminergic drugs, particularly CNS stimulants (e.g., Middaugh, Boggan, & Shepherd, 1994). The value of these studies in animals depends on how well specific behavioral actions of drugs in animals may be relevant to particular cognitive or behavioral outcomes in children (Hannigan & Randall, 1996). Altered behavioral responses to selective dopaminergic drugs, for example, suggested that mesolimbic and nigrostriatal dopamine function was affected persistently
Modification of Alcohol-Related Neurodevelopmental Disorders
(e.g., Becker, Hale, Boggan, & Randall, 1993; Hannigan & Pilati, 1991). While dopamine dysfiinction may underlie locomotor hyperactivity in rodents, and perhaps contribute to attentional problems in FAS children, these types of studies to date have not presented convincing evidence that the neurobehavioral delays and behavioral dysfunctions in FAS/ARND would be ameliorated by specific psychopharmacological treatments (e.g., Hanni-gan & Randall, 1996). The spontaneous locomotor overactivity in rodents, for example, is exacerbated by methylphenidate (Ritalin®) or amphetamine (Dexadrine®; Blanchard, Hannigan, & Riley, 1987; Ulug & Riley, 1983). Perhaps drugs able to facilitate global cognitive functioning, such as novel peptide nootropics (Voronina, 1992), would be more effective in treating ARNDs (Ostrovskaya et al., 1996). Environmental Enrichment Rearing animals in enriched environments is one example of a non-pharmacological global manipulation able to ameliorate ARNDs. Enrichment can reliably stimulate CNS development, facilitate recovery of function, and enhance behavioral performance. We are now systemically examining the effects of postnatal environmental enrichment on brain development and behavior in rats exposed prenatally to alcohol (Hannigan, Berman, & Zajac, 1993). The project aims to assess attenuation of the neurobehavioral sequelae of prenatal alcohol exposure in rats. We and others reported that rearing rats in an enriched environment after prenatal alcohol exposure significantly improved Morris water maze acquisition and ameliorated deficits in motor performance (Hannigan et al., 1993; Wainwright, Levesque, Krempulec, BulmanFleming, & McCutcheon, 1993; see also Goodlett & Johnson, chapter 4, this volume). In neuroanatomical studies, however, enrichment did not reverse decreased neocortical thickness in prenatal alcohol-exposed mice (Wainwright et al., 1993). We examined the hippocampus because it is particularly sensitive to perinatal alcohol as seen, for example, in reduced numbers of CA1 hippocampal pyramidal cells (Barnes & Walker, 1981), aberrant mossy fiber proliferation (West, Hodges, & Black, 1988), and decreased field potentials in CA1 (Krahl et al., in press). Ferrer, Galofre, Lopez-Tejero, and Llobera (1988) reported reduced hippocampal dendritic spine densities in young (postnatal day 15 [PD15]) but not adult (PD90) prenatal alcohol-exposed rats, suggesting the possibility of recovery during postnatal development. We recently reported that environmental enrichment produced gender-influenced increases in apical and basilar dendritic spine density in hippocampal area CA1 pyramidal cells in control rats, but that the effects of this 10-week enrichment experience were absent in the hippocampus of rats that had been exposed prenatally to alcohol (Berman, Hannigan, Sperry, & Zajac, 1996). Briefly, pregnant animals were given 6 g/kg alcohol per day, in two intubations per day, on gestational day 8 (GD8) through GD19. Animals in an intubated control group (0 g/kg ethanol) were intubated with an isocaloric vehicle with sucrose substituted for ethanol, and an untreated control group was not intubated. At weaning on postnatal day 21 (PN21), pups from each prenatal treatment group were assigned to one of two postnatal environmental rearing conditions—isolated or enriched—for about 10 weeks. In the isolated condition, pups were housed individually in hanging steel wire cages with ad lib feed and water, and weighed once per week. Rats in the enriched condition were housed
36 Alcohol and Alcoholism in same-sex groups of 10 to 12 animals from each of the three prenatal treatment groups. The enriched environment arenas were large Nalgene® tubs (75!75!60 cm high) with hardwood chip bedding, feed and water sources, and several “toys” (e.g., dowels, pieces of astroturf, plastic pipe, ladders, etc.) that the animals could manipulate, chew, and climb on. About PN105, offspring were weighed, anesthetized deeply, and perfused transcardially with 0.9% saline/10% phosphate buffered formalin. The fixed brains were removed and 4-mm thick coronal brain sections taken from the dorsal hippocampus. Slices were processed according to a modified version of the rapid Golgi method, embedded in paraffin, and sectioned serially (120 "m). These corona l sections were analyzed
FIG. 3.1. Dendritic spines in hippocampus. The mean (±SEM) dendritic spine densities on apical and basilar tertiary dendrites in CA region of hippocampus in rats exposed prenatally to alcohol (black bars) or sucrose (grey bars), or untreated (open bars). There were no differences among groups raised in the Isolated condition (left). Enriched control groups (on right) had increased spine densities, but the Alcohol group did not. a=significantly different from respective isolated group (p