Sandra J. Kelly

Effects of prenatal alcohol exposure on social behavior in humans and other species

Alcohol exposure during development causes central nervous system alterations in both humans and animals. Although the most common behavioral manifestation of these alterations is a reduction in cognitive abilities, it is becoming increasingly apparent that deficits in social behavior may be very prevalent sequelae of developmental alcohol exposure. In infancy and early childhood, deficits in attachment behavior and state regulation are seen in both alcohol-exposed people and animals, suggesting that these changes are largely the result of the alcohol exposure rather than maternal behavior. In the periadolescent period, people exposed to alcohol during development show a variety of difficulties in the social domain as measured by checklists filled out by either a parent or teacher. Rats exposed to alcohol during development show changes in play and parenting behaviors. In adulthood, prenatal alcohol exposure is related to high rates of trouble with the law, inappropriate sexual behavior, depression, suicide, and failure to care for children. These high rates all suggest that there may be fundamental problems in the social domain. In other animals, perinatal alcohol exposure alters aggression, active social interactions, social communication and recognition, maternal behavior, and sexual behavior in adults. In conclusion, research suggests that people exposed to alcohol during development may exhibit striking changes in social behavior; the animal research suggests that these changes may be largely the result of the alcohol insult and not the environment.

Critical periods for ethanol-induced cell loss in the hippocampal formation

Rodent models of fetal alcohol syndrome (FAS) have revealed discrepant findings in ethanols (EtOH) ability to alter the survival of principal neurons within hippocampal areas CA1, CA3 and the dentate gyrus (DG). One issue is the lack of systematic examination of the timing of EtOH exposure over key periods of hippocampal cell development. The present study examined whether systematic developmental EtOH exposure produces long-term hippocampal cell loss that is related to a specific time course in which either generation, migration or synaptogenic events in this neural region occurs. EtOH treatment occurred during the periods equivalent to the first, second, third and all three trimesters in humans using similar administration procedures for both mothers and pups. Unbiased stereological estimates of the total number of pyramidal and granule cells within hippocampal regions CA1, CA3 and DG were performed when rats reached adulthood. The findings confirm previous reports that area CA1 is highly susceptible to EtOH exposure that occurs during either the early neonatal period or all three trimesters equivalent, while areas CA3 and DG are more resistant to EtOH-induced insult during all periods of hippocampal development examined.

Gender Differences in Brain and Behavior: Hormonal and Neural Bases

This article briefly discusses the difficulties in determining the brain-behavior relationship and reviews the literature on some potential mechanisms underlying gender differences in behavioral responses. Mechanisms that are discussed include genetic effects, organizational effects of gonadal hormones, genomic actions of steroids, nongenomic effects of steroids, and environmental influences. The review is an introduction to the articles presented in this special volume on gender differences in brain and behavior.

Vitamin E protects against alcohol-induced cell loss and oxidative stress in the neonatal rat hippocampus.

Oxidative stress has been proposed as a possible mechanism underlying nervous system deficits associated with Fetal Alcohol Syndrome (FAS). Current research suggests that antioxidant therapy may afford some level of protection against the teratogenic effects of alcohol. This study examined the effectiveness of antioxidant treatment in alleviating biochemical, neuroanatomical, and behavioral effects of neonatal alcohol exposure. Neonatal rats were administered alcohol (5.25 g/kg) by intragastric intubation on postnatal days 7, 8, and 9. A subset of alcohol‐exposed pups were co‐administered a high dose of Vitamin E (2 g/kg, or 71.9 IU/g). Controls consisted of a non‐treated group, a group given the administration procedure only, and a group given the administration procedure plus the Vitamin E dose. Ethanol‐exposed animals showed impaired spatial navigation in the Morris water maze, a decreased number of hippocampal CA1 pyramidal cells, and higher protein carbonyl formation in the hippocampus than controls. Vitamin E treatment alleviated the increase in protein carbonyls and the reduction in CA1 pyramidal cells seen in the ethanol‐exposed group. However, the treatment did not improve spatial learning in the ethanol‐exposed animals. These results suggest that while oxidative stress‐related neurodegeneration may be a contributing factor in FAS, the antioxidant protection against alcohol‐induced oxidative stress and neuronal cell loss in the rat hippocampus does not appear to be sufficient to prevent the behavioral impairments associated with FAS. Our findings underscore the complexity of the pathogenesis of behavioral deficits in FAS and suggest that additional mechanisms beyond oxidative damage of hippocampal neurons also contribute to the disorder.

Critical periods for the effects of alcohol exposure on brain weight, body weight, activity and investigation.

Using an animal model of fetal alcohol syndrome - which equates peak blood alcohol concentrations across different developmental periods - critical periods for the effect of alcohol on brain weight, activity and investigative behavior were examined. The periods of alcohol exposure were from gestational day (GD) 1 through 10, GD 11 through 22, postnatal day (PD) 2 through 10, or all three periods combined. The critical period of alcohol exposure for an increase in activity in juveniles was GD 11 through 22. This pattern was not seen in the same animals in adulthood; instead, increases in both activity and investigation were seen in animals exposed from PD 2 through 10 and not seen in animals exposed during all three periods combined. Brain weight was reduced by alcohol exposure from GD 11 through 22, PD 2 through 10 and all three periods combined. The period from PD 2 through 10 was the only period when the brain weight to body weight ratio was reduced. In conclusion, exposure to alcohol during the periods in the latter half of gestation or early postnatal period seem to have the most deleterious effects on the brain, activity and investigation in the rat. In addition, the effects of alcohol exposure over both the prenatal and postnatal period cannot be easily predicted from the effects of shorter periods of exposure.

Choline Supplementation and DNA Methylation in the Hippocampus and Prefrontal Cortex of Rats Exposed to Alcohol During Development

BACKGROUND Some of the most frequent deficits seen in children with fetal alcohol spectrum disorders (FASD) and in animal models of FASD are spatial memory impairments and impaired executive functioning, which are likely related to alcohol-induced alterations of the hippocampus and prefrontal cortex (PFC), respectively. Choline, a nutrient supplement, has been shown in a rat model to ameliorate some of alcohols teratogenic effects, and this effect may be mediated through cholines effects on DNA methylation. METHODS Alcohol was given by intragastric intubation to rat pups during the neonatal period (postnatal days 2 to 10) (ET group), which is equivalent to the third trimester in humans and a period of heightened vulnerability of the brain to alcohol exposure. Control groups included an intubated control group given the intubation procedure without alcohol (IC) and a nontreated control group (NC). Choline or saline was administered subcutaneously to each subject from postnatal days 2 to 20. On postnatal day 21, the brains of the subjects were removed and assayed for global DNA methylation patterning as measured by chemiluminescence using the cpGlobal assay in both the hippocampal region and PFC. RESULTS Alcohol exposure caused hypermethylation in the hippocampus and PFC, which was significantly reduced after choline supplementation. In contrast, control animals showed increases in DNA methylation in both regions after choline supplementation, suggesting that choline supplementation has different effects depending upon the initial state of the brain. CONCLUSIONS This study is the first to show changes in global DNA methylation of the hippocampal region and PFC after neonatal alcohol exposure. Choline supplementation impacts global DNA methylation in these 2 brain regions in alcohol-exposed and control animals in a differential manner. The current findings suggest that both alcohol and choline have substantial impact on the epigenome in the PFC and hippocampus, and future studies will be needed to describe which gene families are impacted in such a way that function of the nervous system is changed.

Hippocampal Insulin Resistance Impairs Spatial Learning and Synaptic Plasticity

Insulin receptors (IRs) are expressed in discrete neuronal populations in the central nervous system, including the hippocampus. To elucidate the functional role of hippocampal IRs independent of metabolic function, we generated a model of hippocampal-specific insulin resistance using a lentiviral vector expressing an IR antisense sequence (LV-IRAS). LV-IRAS effectively downregulates IR expression in the rat hippocampus without affecting body weight, adiposity, or peripheral glucose homeostasis. Nevertheless, hippocampal neuroplasticity was impaired in LV-IRAS–treated rats. High-frequency stimulation, which evoked robust long-term potentiation (LTP) in brain slices from LV control rats, failed to evoke LTP in LV-IRAS–treated rats. GluN2B subunit levels, as well as the basal level of phosphorylation of GluA1, were reduced in the hippocampus of LV-IRAS rats. Moreover, these deficits in synaptic transmission were associated with impairments in spatial learning. We suggest that alterations in the expression and phosphorylation of glutamate receptor subunits underlie the alterations in LTP and that these changes are responsible for the impairment in hippocampal-dependent learning. Importantly, these learning deficits are strikingly similar to the impairments in complex task performance observed in patients with diabetes, which strengthens the hypothesis that hippocampal insulin resistance is a key mediator of cognitive deficits independent of glycemic control.

Alcohol exposure during development: Impact on the epigenome

Fetal alcohol spectrum disorders represent a wide range of symptoms associated with in utero alcohol exposure. Animal models of FASD have been useful in determining the specific neurological consequences of developmental alcohol exposure, but the mechanisms of those consequences are unclear. Long‐lasting changes to the epigenome are proposed as a mechanism of alcohol‐induced teratogenesis in the hippocampus. The current study utilized a three‐trimester rodent model of FASD to examine changes to some of the enzymatic regulators of the epigenome in adolescence. Combined pre‐ and post‐natal alcohol exposureresulted in a significant increase in DNA methyltransferase activity (DNMT), without affecting histone deacetylase activity (HDAC). Developmental alcohol exposure also caused a change in gene expression of regulators of the epigenome, in particular, DNMT1, DNMT3a, and methyl CpG binding protein 2 (MeCP2). The modifications of the activity and expression of epigenetic regulators in the hippocampus of rodents perinatally exposed to alcohol suggest that alcohols impact on the epigenome and its regulators may be one of the underlying mechanisms of alcohol teratogenesis.

Animal models of fetal alcohol spectrum disorders: Impact of the social environment

Animal models of fetal alcohol spectrum disorder (FASD) have been used to demonstrate the specificity of alcohols teratogenic effects and some of the underlying changes in the central nervous system (CNS) and, more recently, to explore ways to ameliorate the effects of alcohol. The main point of this review is to highlight research findings from the animal literature which point to the impact of the social context or social behavior on the effect(s) of alcohol exposure during development, and also to point to research questions about the social environment and effects of prenatal alcohol exposure that remain to be answered. Alcohol exposure during early development alters maternal responding to the exposed pup in a variety of ways and the alteration in maternal responding could alter later stress responsivity and adult maternal and social behavior of the exposed offspring. Environmental enrichment and voluntary exercise have been shown to ameliorate some of alcohols impact during development, but the roles of enhanced social interactions in the case of enrichment and of social housing during voluntary exercise need to be more fully delineated. Similarly, the role of social context across the lifespan, such as social housing, social experiences, and contact with siblings, needs further study. Because of findings that alcohol during development alters DNA methylation patterns and that there are alterations in the maternal care of the alcohol-exposed offspring, epigenetic effects and their relationship to social behavior in animal models of FASD are likely to become a fruitful area of research. Because of the simpler social behavior and the short lifespan of rodents, animal models of FASD can be useful in determining how the social context impacts the effects of alcohol exposure during development.

Sexually Dimorphic Effects of Perinatal Alcohol Exposure on Social Interactions and Amygdala DNA and DOPAC Concentrations

The hypotheses that exposure of rats to alcohol during a period roughly equivalent to the human third trimester induces changes in social interactions and neurotransmitter and DNA concentrations in the amygdala region were examined. The alcohol exposure was accomplished via an artificial rearing procedure. There were two alcohol-exposed groups (3 and 5 g/kg/day of ethanol) and two control groups (one artificially reared but not exposed to alcohol and one reared normally by dams) in all studies. Active social interactions were reduced in the male 5 g/kg/day group and increased in both female alcohol-exposed groups compared to their respective control groups. Exposure to 5 g/kg/day of alcohol reduced the DNA concentration in the amygdala region of male rats compared to either control group; there were no effects in females. Because some systems have been shown to exhibit alcohol-induced changes only under stressed conditions, noradrenaline, dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC), serotonin, and 5-hydroxyindoleacetic acid (5-HIAA) concentrations were measured in the amygdala region under both nonstressed and stressed conditions. The stress-induced increase in DOPAC concentrations was enhanced in the female high dose group compared to either control group; there were no effects in males. In summary, alcohol exposure during the early postnatal period altered social interactions and DOPAC and DNA concentrations in the amygdala region in a sexually dimorphic manner.