Differential deficits in regional brain growth induced by postnatal alcohol

Murine Models for the Study of Fetal Alcohol Spectrum Disorders: An Overview

Prenatal alcohol exposure is associated to different physical, behavioral, cognitive, and neurological impairments collectively known as fetal alcohol spectrum disorder. The underlying mechanisms of ethanol toxicity are not completely understood. Experimental studies during human pregnancy to identify new diagnostic biomarkers are difficult to carry out beyond genetic or epigenetic analyses in biological matrices. Therefore, animal models are a useful tool to study the teratogenic effects of alcohol on the central nervous system and analyze the benefits of promising therapies. Animal models of alcohol spectrum disorder allow the analysis of key variables such as amount, timing and frequency of ethanol consumption to describe the harmful effects of prenatal alcohol exposure. In this review, we aim to synthetize neurodevelopmental disabilities in rodent fetal alcohol spectrum disorder phenotypes, considering facial dysmorphology and fetal growth restriction. We examine the different neurodevelopmental stages based on the most consistently implicated epigenetic mechanisms, cell types and molecular pathways, and assess the advantages and disadvantages of murine models in the study of fetal alcohol spectrum disorder, the different routes of alcohol administration, and alcohol consumption patterns applied to rodents. Finally, we analyze a wide range of phenotypic features to identify fetal alcohol spectrum disorder phenotypes in murine models, exploring facial dysmorphology, neurodevelopmental deficits, and growth restriction, as well as the methodologies used to evaluate behavioral and anatomical alterations produced by prenatal alcohol exposure in rodents.

Effects of prenatal alcohol exposure (PAE): insights into FASD using mouse models of PAE

The potential impact of prenatal alcohol exposure (PAE) varies considerably among exposed individuals, with some displaying serious alcohol-related effects and many others showing few or no overt signs of fetal alcohol spectrum disorder (FASD). In animal models, variables such as nutrition, genetic background, health, other drugs, and stress, as well as dosage, duration, and gestational timing of exposure to alcohol can all be controlled in a way that is not possible in a clinical situation. In this review we examine mouse models of PAE and focus on those with demonstrated craniofacial malformations, abnormal brain development, or behavioral phenotypes that may be considered FASD-like outcomes. Analysis of these data should provide a valuable tool for researchers wishing to choose the PAE model best suited to their research questions or to investigate established PAE models for FASD comorbidities. It should also allow recognition of patterns linking gestational timing, dosage, and duration of PAE, such as recognizing that binge alcohol exposure(s) during early gestation can lead to severe FASD outcomes. Identified patterns could be particularly insightful and lead to a better understanding of the molecular mechanisms underlying FASD.

Differential Contributions of Alcohol and the Nicotine-Derived Nitrosamine Ketone (NNK) to Insulin and Insulin-Like Growth Factor Resistance in the Adolescent Rat Brain

AIMS

Since epidemiologic studies suggest that tobacco smoke toxins, e.g. the nicotine-derived nitrosamine ketone (NNK) tobacco-specific nitrosamine, can be a co-factor in alcohol-related brain disease (ARBD), we examined the independent and additive effects of alcohol and NNK exposures on spatial learning/memory, and brain insulin/IGF signaling, neuronal function and oxidative stress.

METHODS

Adolescent Long Evans rats were fed liquid diets containing 0 or 26% caloric ethanol for 8 weeks. During weeks 3-8, rats were treated with i.p. NNK (2 mg/kg, 3×/week) or saline. In weeks 7-8, ethanol groups were binge-administered ethanol (2 g/kg; 3×/week). In week 8, at 12 weeks of age, rats were subjected to Morris Water Maze tests. Temporal lobes were used to assess molecular indices of insulin/IGF resistance, oxidative stress and neuronal function.

RESULTS

Ethanol and NNK impaired spatial learning, and NNK ± ethanol impaired memory. Linear trend analysis demonstrated worsening performance from control to ethanol, to NNK, and then ethanol + NNK. Ethanol ± NNK, caused brain atrophy, inhibited insulin signaling through the insulin receptor and Akt, activated GSK-3β, increased protein carbonyl and 3-nitrotyrosine, and reduced acetylcholinesterase. NNK increased NTyr. Ethanol + NNK had synergistic stimulatory effects on 8-iso-PGF-2α, inhibitory effects on p-p70S6K, tau and p-tau and trend effects on insulin-like growth factor type 1 (IGF-1) receptor expression and phosphorylation.

CONCLUSIONS

Ethanol, NNK and combined ethanol + NNK exposures that begin in adolescence impair spatial learning and memory in young adults. The ethanol and/or NNK exposures differentially impair insulin/IGF signaling through neuronal growth, survival and plasticity pathways, increase cellular injury and oxidative stress and reduce expression of critical proteins needed for neuronal function.

Sustained Impairments in Brain Insulin/IGF Signaling in Adolescent Rats Subjected to Binge Alcohol Exposures during Development

Background

Chronic or binge ethanol exposures during development can cause fetal alcohol spectrum disorder (FASD) which consists of an array of neurobehavioral deficits, together with structural, molecular, biochemical, and neurotransmitter abnormalities in the brain. Previous studies showed that perinatal neurodevelopmental defects in FASD are associated with inhibition of brain insulin and insulin-like growth factor (IGF) signaling. However, it is not known whether sustained abnormalities in adolescent brain structure and function are mediated by the same phenomena.

Aims

Using an early postnatal (3^rd trimester equivalent) binge ethanol exposure model, we assessed neurobehavioral function, structure, and the integrity of insulin/IGF signaling in young adolescent cerebella.

Methods

Long Evans male rats were treated with 50 µl of saline (vehicle) or 2 mg/kg of ethanol by i.p. injection on postnatal days (P) 2, 4, 6, and 8. On P19–20, rats were subjected to rotarod testing of motor function, and on P30, they were sacrificed to harvest cerebella for histological, molecular, and biochemical studies.

Results

Binge ethanol exposures impaired motor function, caused sustained cerebellar hypocellularity, and reduced neuronal and oligodendrocyte gene expression. These effects were associated with significant deficits in insulin and IGF signaling, including impaired receptor binding, reduced Akt, and increased GSK-3β activation.

Conclusions

FASD-associated neurobehavioral, structural, and functional abnormalities in young adolescent brains may be mediated by sustained inhibition of insulin/IGF-1 signaling needed for cell survival, neuronal plasticity, and myelin maintenance.

Prenatal ethanol exposure attenuates GABAergic inhibition in basolateral amygdala leading to neuronal hyperexcitability and anxiety-like behavior of adult rat offspring

Prenatal exposure to a relatively high-dose ethanol (EtOH) caused anxiety-like behavior of adult male rat offspring. Previous studies have demonstrated that GABA system in the basolateral amygdala complex (BLA) is involved in the pathogensis of anxiety-related disorders. The role of GABAergic system in the BLA was investigated in anxiety-like behavior evoked by prenatal EtOH exposure. The infusion of midazolam (MDZ), a positive modulator of GABA(A) receptor, into the BLA prevented anxiety-like behavior in EtOH-offspring without affecting the corresponding behavior of control offspring. The data suggest that anxiety-like behavior could be causally related to increased neuronal excitability attributable to depressed GABAergic inhibition in the BLA. To test this hypothesis, evoked potential was studied using brain slices from EtOH-offspring. Potential evoked in the BLA by single stimuli applied to external capsule showed multispike responses, indicative of GABAergic disinhibition. These multiple responses were no longer evident after the perfusion with MDZ. In the slices from EtOH-offspring, paired-pulse inhibition (GABA(A)-dependent) was suppressed. Also, in EtOH-offspring, long-term potentiation (LTP) was induced by a single train of high frequency stimulation, which did not induce LTP in control rats. Moreover, MDZ pretreatment prevented the facilitating effect of EtOH on LTP induction. The data provide the functional evidence that prenatal EtOH exposure attenuates GABAergic inhibition in the BLA resulting in neuronal hyperexcitability and anxiety-like behavior of adult rat offspring.

Effects of exogenous agents on brain development: stress, abuse and therapeutic compounds

The range of exogenous agents likely to affect, generally detrimentally, the normal development of the brain and central nervous system defies estimation although the amount of accumulated evidence is enormous. The present review is limited to certain types of chemotherapeutic and "use-and-abuse" compounds and environmental agents, exemplified by anesthetic, antiepileptic, sleep-inducing and anxiolytic compounds, nicotine and alcohol, and stress as well as agents of infection; each of these agents have been investigated quite extensively and have been shown to contribute to the etiopathogenesis of serious neuropsychiatric disorders. To greater or lesser extent, all of the exogenous agents discussed in the present treatise have been investigated for their influence upon neurodevelopmental processes during the period of the brain growth spurt and during other phases uptill adulthood, thereby maintaining the notion of critical phases for the outcome of treatment whether prenatal, postnatal, or adolescent. Several of these agents have contributed to the developmental disruptions underlying structural and functional brain abnormalities that are observed in the symptom and biomarker profiles of the schizophrenia spectrum disorders and the fetal alcohol spectrum disorders. In each case, the effects of the exogenous agents upon the status of the affected brain, within defined parameters and conditions, is generally permanent and irreversible.

Magnetic resonance microscopy defines ethanol-induced brain abnormalities in prenatal mice: effects of acute insult on gestational day 8

BACKGROUND

Magnetic resonance microscopy (MRM), magnetic resonance imaging (MRI) at microscopic levels, provides unprecedented opportunities to aid in defining the full spectrum of ethanol's insult to the developing brain. This is the first in a series of reports that, collectively, will provide an MRM-based atlas of developmental stage-dependent structural brain abnormalities in a Fetal Alcohol Spectrum Disorders (FASD) mouse model. The ethanol exposure time and developmental stage examined for this report is gestational day (GD) 8 in mice, when the embryos are at early neurulation stages; stages present in humans early in the fourth week postfertilization.

METHODS

For this study, pregnant C57Bl/6J mice were administered an ethanol dosage of 2.8 g/kg intraperitoneally at 8 days, 0 hour and again at 8 days, 4 hours postfertilization. On GD 17, fetuses that were selected for MRM analyses were immersion fixed in a Bouin's/Prohance solution. Control fetuses from vehicle-treated dams were stage-matched to those that were ethanol-exposed. The fetal mice were scanned ex vivo at 7.0 T and 512 x 512 x 1024 image arrays were acquired using 3-D spin warp encoding. The resulting 29 microm (isotropic) resolution images were processed using ITK-SNAP, a 3-D segmentation/visualization tool. Linear and volume measurements were determined for selected brain, head, and body regions of each specimen. Comparisons were made between control and treated fetuses, with an emphasis on determining (dis)proportionate changes in specific brain regions.

RESULTS

As compared with controls, the crown-rump lengths of stage-matched ethanol-exposed GD 17 fetuses were significantly reduced, as were brain and whole body volumes. Volume reductions were notable in every brain region examined, with the exception of the pituitary and septal region, and were accompanied by increased ventricular volumes. Disproportionate regional brain volume reductions were most marked on the right side and were significant for the olfactory bulb, hippocampus, and cerebellum; the latter being the most severely affected. Additionally, the septal region and the pituitary were disproportionately large. Linear measures were consistent with those of volume. Other dysmorphologic features noted in the MR scans were choanal stenosis and optic nerve coloboma.

CONCLUSIONS

This study demonstrates that exposure to ethanol occurring in mice at stages corresponding to the human fourth week postfertilization results in structural brain abnormalities that are readily identifiable at fetal stages of development. In addition to illustrating the utility of MR microscopy for analysis of an FASD mouse model, this work provides new information that confirms and extends human clinical observations. It also provides a framework for comparison of structural brain abnormalities resulting from ethanol exposure at other developmental stages and dosages.

Ethanol exposure of neonatal rats does not increase biomarkers of oxidative stress in isolated cerebellar granule neurons

Oxidative stress is a candidate mechanism for ethanol neuropathology in fetal alcohol spectrum disorders. Oxidative stress often involves production of reactive oxygen species (ROS), deterioration of the mitochondrial membrane potential (MMP), and cell death. Previous studies have produced conflicting results regarding the role of oxidative stress and the benefit of antioxidants in ethanol neuropathology in the developing brain. This study investigated the hypothesis that ethanol neurotoxicity involves production of ROS with negative downstream consequences for MMP and neuron survival. This was modeled in neonatal rats at postnatal day 4 (P4) and P14. It is well established that granule neurons in the rat cerebellar cortex are more vulnerable to ethanol neurotoxicity on P4 than at later ages. Thus, it was hypothesized that ethanol produces more oxidative stress and its negative consequences on P4 than on P14. A novel experimental approach was used in which ethanol was administered to animals in vivo (gavage 6g/kg), granule neurons were isolated 2-24h post-treatment, and ROS production and relative MMP were immediately assessed in the viable cells. Cells were also placed in culture and survival was measured 24h later. The results revealed that ethanol did not induce granule cells to produce ROS, cause deterioration of neuronal MMP, or cause neuron death when compared to vehicle controls. Further, granule neurons from neither P4 nor P14 animals mounted an oxidative response to ethanol. These findings do not support the hypothesis that oxidative stress is obligate to granule neuron death after ethanol exposure in the neonatal rat brain. Other investigators have reached a similar conclusion using either brain homogenates or cell cultures. In this context, it is likely that oxidative stress is not the sole and perhaps not the principal mechanism of ethanol neurotoxicity for cerebellar granule neurons during this stage of brain development.

Protective effects of erythropoietin against ethanol-induced apoptotic neurodegenaration and oxidative stress in the developing C57BL/6 mouse brain

The developing central nervous system is extremely sensitive to ethanol, with well-defined temporal periods of vulnerability. Recent studies have shown that administration of ethanol to infant rats during the synaptogenesis period triggers extensive apoptotic neurodegeneration throughout many regions of the developing brain. Furthermore, acute ethanol administration produces lipid peroxidation in the brain as an indicator of oxidative stress. In recent years, it has been shown that erythropoietin (EPO) has a critical role in the development, maintenance, protection, and repair of the nervous system. In the present study, we investigated the effect of EPO against ethanol-induced neurodegeneration and oxidative stress in the developing C57BL/6 mouse brain. Seven-day-old C57BL/6 mice were divided into three groups: control group, saline-treated group, EPO-treated group. Ethanol was administered to mice at a dosage of 2.5 g/kg for two times with a 2-h interval. Recombinant human EPO (rhEPO) was given 1000 U/kg. Twenty-four hours after the first dose of ethanol, all the animals were killed. Neuronal cell death, apoptosis, thiobarbituric acid substance (TBARS) levels, superoxide dismutase (SOD), and glutathione peroxidase (Gpx) enzymes activities were evaluated. Histopathological evaluation demonstrated that EPO significantly diminished apoptosis in the cerebellum, prefrontal cortex, and hippocampus and also spared hippocampal CA1, CA2, and CA3 neurons. Simultaneous administration of EPO along with ethanol attenuated the lipid peroxidation process and restored the levels of antioxidants. Regarding the wide use of erythropoietin in premature newborns, this agent may be potentially beneficial in treating ethanol-induced brain injury in the perinatal period.

Early postnatal exposure to alcohol reduces the number of neurons in the occipital but not the parietal cortex of the rat

BACKGROUND

The rat brain undergoes a period of rapid growth in the early postnatal period. During this time, the neocortex seems to be vulnerable to ethanol injury. Subdivisions of the neocortex develop in a temporospatial gradient that is likely to determine their vulnerability to ethanol-induced damage and whether damage is permanent. Therefore, the authors investigated the effect of postnatal ethanol exposure on the neocortex and specific subregions at the cessation of exposure and in the mature brain.

METHODS

Four-day-old rat pups with intragastric cannulae were artificially reared from postnatal day (PN) 4 through PN9. Of 12 daily feeds, two consecutive feeds contained either ethanol (4.5 g/kg) or an isocaloric maltose/dextrin solution. On PN10 or PN115, animals were perfused intracardially, and the brains were removed. Stereological methods were used to determine the total number of neurons and glial cells in, and the volume of, the neocortex, the parietal cortex, and the occipital cortex.

RESULTS

Exposure to ethanol did not affect body or brain weight at PN10. In contrast, at PN115 forebrain weight was significantly lower in ethanol-exposed animals compared with control-treated animals. There was no effect of treatment on body weight at PN115. On PN10, neocortical volume was 15% smaller in the ethanol-exposed animals compared with controls, with no change in the total number of neurons or glial cells. Occipital cortical volume was reduced by 22% in the ethanol-exposed animals, with a significant deficit in the total number of neurons (ethanol-exposed, 2.62 x 10; gastrostomy control, 3.20 x 10). There was no effect of ethanol exposure on the total number of glial cells in the occipital cortex or on any parameter in the parietal cortex. There was also no significant effect of ethanol exposure on the occipital cortex on PN115.

CONCLUSIONS

These findings provide support for the hypothesis that a specific area or cell population might be differentially vulnerable to ethanol exposure during the brain growth spurt and that cell deficits evident on PN10 may not be permanent.

Effects of alcohol exposure during development on social behavior in rats

In addition to the cognitive deficits associated with fetal alcohol syndrome (FAS), clinical and animal studies indicate that alcohol exposure might also have detrimental effects on social behavior. In a rat model of FAS, experimental rats were given alcohol from gestational day (GD) 1 to 22 and from postnatal day (PD) 2 to 10, a period roughly equivalent to all three trimesters in humans. Control groups consisted of rats exposed to the administration procedures but not to alcohol and nontreated rats. At 30 days of age, rats were tested for social behavior in an alley maze that contained its cagemate in the goal box. After varying periods of isolation, the animals' latencies to reach the goal box and their social behaviors once inside the goal box were recorded. Alcohol-exposed animals ran faster than control rats to the occupied goal box regardless of the amount of isolation. The alcohol-exposed animals also exhibited aberrant social interactions with their cagemate once inside the goal box compared to one or both of the control groups. Specifically, the alcohol-exposed animals showed greater amounts of anogenital sniffing, chasing, hopping and darting, and retrieving and lesser amounts of pinning and biting compared to one or both of the control groups. The alcohol-induced change in anogenital sniffing varied over increasing amounts of isolation compared to both control groups, but the alterations in the other behaviors did not. It is argued that the altered social behavior of alcohol-exposed animals is not the result of changes in the animals' motivational state or social learning and may be the result of an increased responsiveness to social stimuli.

Increased cell death in the developing vestibulocochlear ganglion complex of the mouse after prenatal ethanol exposure

BACKGROUND

Previous studies have demonstrated that excessive prenatal alcohol exposure can damage the auditory and vestibular systems, in particular, cochlear hair cells. However, the direct effect of ethanol on the peripheral neurons in these pathways has not been examined. To study the effects of prenatal ethanol exposure on the developing vestibulocochlear ganglion (VCG) complex and the peripheral sensory organs, we exposed pregnant mice to ethanol and examined the levels of cell death in the inner ear.

METHODS

Pregnant C57BL/6J mice were administered one of three doses of either ethanol (3.0, 4.5, and 5.5 g/kg) or isocaloric maltose/dextrin via intragastric intubation on gestational day (GD) 12.5. Embryos were dissected out of the uterus 8 hr after the intubation. Dying cells in the inner ear were stained with Nissl stain and labeled by in situ terminal dUTP nick-end labeling (TUNEL), and the percentage of dying cells was quantified.

RESULTS

Ethanol exposure produced region-specific effects, with ethanol-exposed embryos exhibiting enhanced cell death only in the VCG complex, and not in the primitive saccule, cochlea, semicircular canal, or endolymphatic sac. The effects of ethanol on cell death in the VCG are dose dependent, with a significant increase in the level of cell death found only at the higher doses.

CONCLUSIONS

Ethanol has a selective cytotoxic dose-dependent effect on the VCG at GD 12.5 suggesting that loss of VCG neurons may contribute to hearing and /or vestibular abnormalities in FAS children. Furthermore, the presence of TUNEL-positive cells and DNA laddering is consistent with the cells undergoing apoptotic cell death.

Effects of postnatal ethanol exposure on brain growth and lipid composition in n-3 fatty acid-deficient and -adequate rats

The artificial rearing model was used to investigate the effects of short-term exposure to ethanol on growth and fatty acid composition of forebrain (FB) and cerebellum (CB) during the brain growth spurt in either n-3 fatty acid-adequate (AD) or n-3 deficient (DEF) rat pups. On postnatal day 5, offspring of female rats that had been fed AD or DEF diets from day 5 of life were assigned to three groups: members of two groups were gastrostomized and artificially fed formulas appropriate for their maternal history, and the third group (suckled control) was fostered to lactating dams of a similar dietary history. Half of the artificially reared pups in each dietary condition were fed ethanol in their formula (7% vol/vol) in one-quarter of their daily feedings, while the others received maltose-dextrin substituted isocalorically for ethanol. Blood alcohol concentrations did not differ between the dietary groups. FB weight on postnatal day 9 was lower in ethanol-exposed offspring in both dietary conditions. Brain fatty acid composition reflected dietary history in that, compared with AD pups, DEF pups had lower percentages of docosahexaenoic acid, higher percentages of 22:5n-6, and a higher n-6/n-3 fatty acid ratio. However, the effects of ethanol exposure were inconsistent, lowering the n-6/n-3 ratio in the phosphatidylethanolamine (PE) fraction in FB but not in CB, while increasing this ratio in the phosphatidylcholine (PC) fraction in FB of the DEF pups only. Thus, while ethanol had some effects on lipid composition, there was no difference between the dietary groups in their vulnerability to the effects of early short-term ethanol exposure on brain growth.

Fetal alcohol exposure and temporal vulnerability: regional differences in cell loss as a function of the timing of binge-like alcohol exposure during brain development

This study was conducted to determine the temporal and regional vulnerability of the brain as a function of exposure to alcohol during brain development. Our goal was to manipulate the timing of alcohol exposure and assess the relative risk of cell loss in two different brain regions. Groups of timed pregnant Sprague-Dawley rats received binge-like alcohol exposure during either the first 10 days (first-trimester equivalent) or second 10 days of gestation (second-trimester equivalent), or the combination of first- and second-trimester equivalents for prenatal treatments. Offspring from some of the animals exposed to alcohol during the combined first- and second-trimester equivalent were reared artificially from postnatal days (P) 4 through 9 (part of the third-trimester equivalent) and also received binge-like alcohol during this period, producing animals that were exposed to alcohol during all three trimesters equivalent. Offspring from untreated dams were also reared artificially and received alcohol from only P4-9, thus creating animals that were exposed to alcohol only during part of the third-trimester equivalent. All pups were perfused on P10. Appropriate controls (nutritional and normally reared) were matched to every alcohol treatment combination. Peak blood alcohol concentrations were not different among the treatment groups for a given sampling time. Total cell numbers in the cerebellum (Purkinje and granule cells) and the olfactory bulb (mitral and granule cells) were estimated by the unbiased stereological technique, the optical disector. In terms of temporal vulnerability, alcohol exposure during the equivalent of all three trimesters resulted in a greater reduction in cerebellar Purkinje cell numbers compared with exposure to alcohol during the third-trimester equivalent, whereas both groups had a significant reduction in cell number compared with all other timing groups. Cerebellar granule cell number was reduced after alcohol exposure during all three trimesters equivalent, compared with all other timing groups. Alcohol exposure during the third-trimester equivalent resulted in a decrement in the number of olfactory bulb mitral cell numbers compared with all other groups, but there were no differences among the timing groups in numbers of olfactory bulb granule cells. When the cell loss in the two regions was compared within each alcohol treatment group to determine the relative regional vulnerability, the primary salient finding was that cerebellar Purkinje cells were more vulnerable to alcohol-induced loss subsequent to exposure during all three trimesters equivalent. No other regional differences were detected. These results extend earlier findings by showing that alcohol exposure during different periods of brain development results in regional differences in cell loss as a function of the timing of alcohol exposure during brain development and illustrate the variability of alcohol-induced neuronal loss.

Ethanol inhibition of brain ornithine decarboxylase activity in the postnatal rat

The purpose of this study was to determine the relationship between ornithine decarboxylase activity (ODC; a marker for perturbed cell development), the blood alcohol level, and alcohol-induced microencephaly in the developing rat brain after binge treatment with ethanol vapour. By manipulating ethanol flow we were able to adjust vapour concentrations (24-65 mg ethanol/l air) such that an acute exposure of ethanol vapour for 3 h resulted in a range of blood alcohol levels (2.3-5.5 mg/ml). Acute studies showed that ethanol dose-dependently inhibited rat hippocampal and cerebellar ODC activity at PND4-PND10. There was a significant correlation between the blood alcohol level and degree of inhibition at all ages tested. Chronic treatment from PND4 to PND9 caused a significant decrease in both brain to body weight ratio and in hippocampal and cerebellar ODC activities at PND10. These results indicate that ethanol-induced disruption in ODC could play a significant role in ethanol's teratogenic effects during early postnatal development.

Effects of neonatal ethanol exposure on cholinergic neurons of the rat medial septum

The objective of this study was to determine the long-term effects of neonatal ethanol exposure on the cholinergic neurons in the medial septum (MS) of the rat. On postnatal day 4 (P4) pups were assigned to one of three groups: an ethanol-receiving, gastrostomized group (EtOH); a pair-fed, gastrostomized control group (GC); and a dam-reared suckle control group (SC). Gastrostomized pups were infused with ethanol-containing or control diet as a 9.1% v/v solution for two feedings on each day from P4 to P10. Choline acetyltransferase (ChAT) immunocytochemistry was analyzed at P60. Ethanol treatment resulted in long-lasting microencephaly in P60 EtOH animals. Ethanol exposure did not directly reduce ChAT-expressing (ChAT+) neuronal number, nor were changes noted in MS volume, mean area/section, or cell density as a result of ethanol treatment. Ethanol exposure reduced ChAT+ neuronal size in EtOH males compared with GC males but not SC males. No differences in ChAT+ neuronal size were noted in females. Thus, neonatal ethanol exposure, whereas producing long-lived microencephaly, has little effect on the cholinergic neurons of the adult rat MS.

Use of inhalation to study the effect of ethanol and ethanol dependence on neonatal mouse development without maternal separation: a preliminary study

This study explored the use of ethanol inhalation as a model to study the effects of ethanol and ethanol dependence on neonatal brain development in mice without maternal separation. In these experiments two day old Swiss Webster mice with their mothers were put in an inhalation chamber and continuously exposed to ethanol vapors for 12 days. The results indicate that: (a) the neonates developed substantial blood ethanol levels (160 to 290 mg/dl); (b) the mothers had minimal blood ethanol concentrations (BECs < 10mg/dl); (c) no mortality was observed during ethanol exposure; (d) physical dependence to ethanol was produced in the neonates, as evidenced by typical withdrawal symptoms.; (e) exposure to ethanol vapors did not affect the weight gain of the neonates indicating that nutrition and suckling ability was not significantly altered; the body weight of the mothers were also not affected; (f) 12 days of neonatal ethanol exposure significantly reduced whole brain and cerebellar weights on postnatal day 45 as compared to the controls; (g) neonatal ethanol exposure resulted in behavioral changes on postnatal day 40 to 41. Twelve days of ethanol exposure significantly impaired habituation, but did not alter spontaneous locomotion and (h) ethanol sensitivity on postnatal day 45 measured by Loss of Righting Reflex (LORR) was not affected. Although further studies are necessary, the results demonstrate that exposure to ethanol vapors can cause high BECs in the neonates without causing meaningful BECs in the mothers. Collectively, the results indicate that the ethanol inhalation technique can be used to investigate the effects of ethanol and ethanol dependence on neonatal development in mice during the rodent equivalent of the human third trimester.

Cocaethylene exposure during the brain growth spurt period: brain growth restrictions and neurochemistry studies

The concurrent use of alcohol and cocaine has recently attracted attention in the medical research field due to the prevalence of this drug abuse pattern and the exclusive formation of a pharmacologically active substance, cocaethylene (CE). This is the first study to examine the neuroteratogenic effects of cocaethylene exposure during the brain growth spurt (part of the third trimester equivalent) on brain growth restrictions and neurochemical profiles. For the brain growth restrictions study, three groups of artificially reared rat pups were given daily injections of 0, 10 or 20 mg/kg cocaethylene (s.c.) from postnatal days (PDs) 4 through 9. One group of normally reared pups (suckle control) also was used. These pups were perfused on PD 10 and the brains were removed and weighed (forebrain, cerebellum and brainstem). For the neurochemistry study, five groups of artificially reared pups were used and were treated identically to those in the brain growth restrictions study, with the exceptions that animals assigned to acute cocaethylene treatment groups did not receive cocaethylene from PDs 4 through 8 and all animals in this study were sacrificed on PD 9 by decapitation. One suckle control group was included to control the possible artificial rearing effects on the neurochemical measures. Blood and fresh brain tissues (cortex, subcortical structures, cerebellum and brainstem) were collected for blood cocaethylene concentration and neurochemical analyses using GC/MS and HPLC techniques, respectively. The statistical analyses indicated that daily administration of 10 or 20 mg/kg cocaethylene, but not 0 mg/kg cocaethylene, significantly restricted the brain growth (brain weights) in all three brain regions assessed. Furthermore, cocaethylene administration from PDs 4 through 9 produced region-specific alterations in various neurotransmitter concentrations. The changes in neurotransmitter levels were not a function of the responses to the last cocaethylene injection on PD 9, since the outcomes between six days of cocaethylene treatment (PDs 4 to 9) and one day acute treatment (PD 9) were notably different. Furthermore, the artificial rearing procedure appeared to produce significant alterations in various neurotransmitter levels when compared with normally reared (suckle) controls. Collectively, these results suggest that cocaethylene is neuroteratogenic to the developing brain during the third trimester equivalent and the unique formation of cocaethylene resulting from the concurrent use of alcohol and cocaine may represent an increased risk to the developing brain beyond the intrinsic neuroteratogenic effects of cocaine and alcohol individually.

Prenatal binge-like alcohol exposure alters neurochemical profiles in fetal rat brain

The majority of studies examining the effects of prenatal exposure to alcohol on neurotransmitter levels have furnished results that are divergent (increase, decrease or no change). The present study assessed six neurochemical compounds [norepinephrine (NE), dopamine (DA), dihydroxyphenylacetic acid (DOPAC), serotonin (5-HT), 5-hydroxyindole acetic acid (5-HIAA), gamma-aminobutyric acid (GABA)] from the same brain tissue. Pregnant Sprague-Dawley rats were given 5.1 g/kg alcohol (by gavage) either daily from embryonic day 1 (E1) through E20 or E20 only. In addition, pairfed/intubated (PF/INT) and ad lib chow (Chow) groups were included as controls. The dams were sacrificed and the fetuses were removed on E20. Binge-like alcohol exposure throughout gestation (E1-E20) produced significantly higher brain to body weight ratios compared with all other groups. Alcohol exposure did not produce changes in NE levels, although the E1-E20 exposure to alcohol reduced the contents of DA and 5-HT compared with the PF/INT and Chow controls. In addition, the E20 alcohol treatment reduced both DA and 5-HT levels compared with the E1-E20 alcohol treatment. DOPAC and 5-HIAA contents were affected by the prenatal treatments insofar as the 5-HIAA levels were decreased in E/1-20 and E20 animals relative to both controls, while the DOPAC levels were decreased in E/1-20, E20 and PF/INT groups compared to the Chow group; however, both metabolites were unaffected by the difference in alcohol treatment duration. Moreover, GABA levels were increased in fetuses exposed to alcohol from E1-E20 compared with all other groups. Collectively, these findings suggest that binge-like alcohol exposure prior to and during neurotransmitter development affects the baseline content of several neurotransmitters.

Long-term effect of postnatal alcohol exposure on the number of cells in the neocortex of the rat: a stereological study

Behavioral and morphological studies suggest that exposure to alcohol during development may cause damage in the neocortex. In this study, rat pups were exposed to alcohol during the brain growth spurt and examined at adulthood to ascertain the long-term effect of alcohol exposure on the neocortex. Four-day-old rat pups were surgically implanted with an intragastric cannula while under ether anesthesia and artificially reared from postnatal day (PN) 4 through PN11. Two of the consecutive 12 daily feeds contained either alcohol (4.5 g/kg; alcohol-exposed) or an isocaloric maltose/dextrin solution (gastrostomy control) from PN4 through PN9. On PN115, animals were perfused intracardially and the brains removed. Unbiased stereological methods were used to determine the neocortical volume, the total number of neurons and glial cells in the entire neocortex and in layer V, and the mean cell volume of neurons or mean nuclear volume of glial cells in layer V. No effect of alcohol was seen in the neuronal population on either cell number or mean cell volume, nor was there any difference in the total number or mean nuclear volume of glial cells in layer V. These findings suggest that neither the entire neocortex nor layer V alone are vulnerable to permanent alcohol-induced cell death.

Combined pre- and postnatal ethanol exposure alters the development of Bergmann glia in rat cerebellum

The development and maturation of Bergmann glial cells in the rat cerebellum was evaluated on postnatal day 15 by glial fibrillary acidic protein (GFAP) immunocytochemistry, following combined gestational and 10-day postnatal ethanol exposure (a full three trimester human equivalency). GFAP-positive Bergmann glial fibers of lobules I, III, VIb, VII and X of the cerebellar vermis were examined and counted in the molecular layer (ML), the external granular layer (EGL) and the external limiting membrane (ELM). Ethanol exposure reduced: (1) the number of GFAP-positive fibers (per unit length of folia surface) at all three levels; (2) the percentage of mature fibers; and (3) the cross-sectional area in all lobules examined. When data from the five lobules were pooled, there were 7% fewer GFAP-positive fibers in the ML, 15% fewer in the EGL and 20% fewer in the ELM; the percentage of mature fibers was reduced by 16%; and the cross-sectional areas of lobules were reduced by 16%. The altered development of Bergmann glia could be one of the factors causing delayed migration of granular neurons and reductions in the number of granule cells reported in other studies following developmental ethanol exposures and could help to explain some of the motor dysfunctions reported in FAS victims.

Eyeblink conditioning in the infant rat: an animal model of learning in developmental neurotoxicology

Classical conditioning of the eyeblink reflex is a relatively simple procedure for studying associative learning that was first developed for use with human subjects more than half a century ago. The use of this procedure in laboratory animals by psychologists and neuroscientists over the past 30 years has produced a powerful animal model for studying the behavioral and biological mechanisms of learning. As a result, eyeblink conditioning is beginning to be pursued as a very promising model for predicting and understanding human learning and memory disorders. Among the many advantages of this procedure are (a) the fact that it can be carried out in the same manner in both humans and laboratory animals; (b) the many ways in which it permits one to characterize changes in learning at the behavioral level; (c) the readiness with which hypotheses regarding the neurological basis of behavioral disorders can be formulated and tested; (d) the fact that it can be used in the same way across the life-span; and (e) its ability to distinguish, from normative groups, populations suffering from neurological conditions associated with impaired learning and memory, including those produced by exposure to neurotoxicants. In this article, we argue that these properties of eyeblink conditioning make it an excellent model system for studying early impairments of learning and memory in developmental neurotoxicology. We also review progress that has been made in our laboratory in developing a rodent model of infant eyeblink conditioning for this purpose.

The effects of the timing of ethanol exposure during the brain growth spurt on the number of cerebellar Purkinje and granule cell nuclear profiles

Ethanol exposure during development is particularly deleterious to cerebellar Purkinje cells and granule cells, but the mechanism(s) underlying this sensitivity and the variables which affect it remain unknown. One important variable that has not been fully investigated, is the timing of the ethanol exposure. Ethanol exposure during the brain growth spurt causes a differential loss of Purkinje cells across the 10 lobules of the vermal cerebellum. However, whether or not changing the timing of the ethanol exposure during the brain growth spurt alters the extent and location of the loss of Purkinje cells within the cerebellar vermis has not been investigated. Moreover, the loss of cerebellar granule cells has been shown to parallel the loss of Purkinje cells, leading to the conclusion that the loss of granule cells occurred as a function of the loss of their targets, the Purkinje cells. The purpose of this study was to address both issues. Male rat pups were exposed to ethanol, via an artificial-rearing method, during one of the following 2-day time periods: postnatal days (PD) 4-5, 5-6, 6-7, 7-8, 8-9, 9-10, or 12-13. Gastrostomy control (GC) and suckle control (SC) groups also were included. All pups were sacrificed on PD21. The number of Purkinje cell nuclear profiles from three vermal sections were counted in all groups, while the number of granule cell nuclear profiles in the ten lobules was estimated from pups in selected groups. No loss of Purkinje cells was observed in pups exposed to ethanol on PD7-8 or at any of the later exposure times. Additionally, among the three exposure groups in which significant Purkinje cell loss was observed (PD4-5, PD5-6 and PD6-7), seven lobules exhibited significant differences particularly between the PD4-5 and PD6-7 groups. The group with the greatest loss of Purkinje cells (PD4-5) also was the group with the greatest loss of granule cells. A significant loss of granule cells did not occur without a corresponding loss of Purkinje cells. The loss of both the Purkinje and granule cells was affected by the timing of the ethanol exposure, and that the extent and the location of Purkinje cell loss were extremely sensitive to the effects of the timing of the ethanol exposure.

Effects of environmental enrichment on cortical depth and Morris-maze performance in B6D2F2 mice exposed prenatally to ethanol

Pregnant mice were fed a liquid diet with 25% of the calories as ethanol from day 5 to 17 of gestation; controls received equivalent amounts of diet with maltose-dextrin substituted isocalorically for the ethanol. Two male weanlings from each litter were assigned randomly to an enriched or isolated environmental condition. After 6 weeks in these environments measures of brain growth were obtained, including thickness of frontal, parietal, and occipital cortex (study 1), or their behavioral capabilities were assessed in a Morris water maze (study 2). Ethanol decreased birth weight (both studies), postweaning body weight (study 2), and brain weight (study 1), while the enriched animals in both studies were heavier. Ethanol decreased the thickness of the occipital cortex only. All groups demonstrated learning by showing a decrease in latency to locate the hidden platform over the 5 days of testing; this was supported by their spending most time in the target quadrant during the probe trial. The latencies of the enriched animals were shorter than the isolated; covariance analysis indicated that this was not due solely to their faster swimming speed.

Effects of prenatal ethanol exposure on the development of Bergmann glia and astrocytes in the rat cerebellum: an immunohistochemical study

The consequences of prenatal ethanol exposure on the postnatal development of Bergmann glia and astrocytes in the rat cerebellum were investigated by using glial fibrillary acidic protein (GFAP) immunolabeling. Pregnant rats were either fed with an ethanol containing liquid diet (6.7% v/v) or pair-fed with an isocaloric diet throughout gestation. On postnatal day (PD) 15 and 22, parasagittal sections of the cerebellar vermis from female offspring were processed for GFAP immunohistochemistry to assess the development of Bergmann glia and astrocytes in lobules I, VII, and X and astrocytes in the central core of white matter. On PD 15, compared to control animals, ethanol exposed animals had fewer GFAP positive Bergmann glial fibers per unit length of molecular layer; a significantly greater percentage of morphologically immature Bergmann fibers; a significantly greater GFAP positive astrocytic area per unit area of internal granular layer and central white matter; and the astrocytic processes were wider and more closely packed. These glial changes were associated with significantly thicker external granular layer in all 3 lobules. However, no significant differences were seen between the ethanol exposed and control animals on PD 22, indicating "catch-up growth" in the ethanol exposed animals during the third postnatal week. These results suggest that prenatal ethanol exposure causes (1) delayed maturation of Bergmann glia, which in turn contributes to the delayed migration of granule cells; and (2) alterations in the normal postnatal development of astrocytes.

Alcohols synergize with NGF to induce early differentiation of PC12 cells

The role of alcohols in affecting neuromorphogenesis was investigated in a single cell type, pheochromocytoma (PC12). The effect of ethanol at physiological concentrations in this system leads to enhanced morphological and functional differentiation in combination with nerve growth factor (NGF). PC12 cells treated with a suboptimal concentration of NGF (30 ng/ml) and an alcohol (87 mM) underwent rapid morphological differentiation which was dependent upon the side chain length of the alcohol MeOH less than EtOH less than PrOH less than BuOH. Pyrazole at either 5 or 10 mM had no effect on alcohol induced neurite extension. Assessment of the degree of differentiation promoted by the various alcohols was quantified by an increase in neurite extension, a decrease in the incorporation of [3H]thymidine, an increase in acetylcholine esterase (AChE) activity and immunostaining with neuron specific enolase. Thus, alcohols may function in a specific manner by interacting with transmembrane signalling pathways which promote gene expression and neuronal differentiation.

Effect of ethanol on the morphohistogenesis and differentiation of cerebellar granule cells in the chick embryo

In this present study we analyse, with the help of the Golgi method, the effect of ethanol on the morphological differentiation of the cerebellar granule cells in the chick embryo. Ethanol seems to affect the process of cell migration from the early stages of differentiation. Some granule cells appear to differentiate in an inverted position. These observations also confirm, on the basis of their axon morphology, the existence of three types of granule cells in the chick cerebellum.

Passive avoidance performance following neonatal alcohol exposure

Prenatal alcohol exposure has been associated with deficits in response inhibition in both human and nonhuman studies. In this study, we investigated the effects of neonatal alcohol exposure on passive avoidance, a task that requires response inhibition. Neonatal alcohol exposure has been used to examine the effects of alcohol during a period of CNS development that is equivalent to the human third trimester "brain growth spurt." Subjects were 23-day-old rats that were artificially reared (AR) from gestation day (GD) 26-32 through gastrostomy tubes. The AR groups included two ethanol doses; 6 g/kg and 4 g/kg and an isocaloric control. A sham surgery group was also included. Subjects were tested for acquisition and 24-hr retention of the passive avoidance task. The 6 g/kg females required more trials to reach the criterion during both acquisition and retention relative to all other groups. These findings suggest that neonatal alcohol exposure can produce deficits in response inhibiton, but that there may be differential sensitivity across sexes to some of alcohol's effects.

Alterations in gait following ethanol exposure during the brain growth spurt in rats

Walking patterns were assessed in rats that had been exposed to alcohol neonatally during a period encompassing the brain growth spurt. Rat pups were exposed via an artificial rearing technique to either a 2.50% (w/v) or 2.15% (w/v) EtOH-milk formula on Days 26-32 postconception. An artificially reared control group and a suckle-control group were also included in the experiment. Gait patterns were assessed in animals from each of the neonatal treatment groups at 43, 67, and 87 days postconception. No differences in gait patterns were evident on Day 43 postconception; however, on Days 67 and 87 animals exposed to alcohol during the neonatal period displayed an abnormal gait. These animals had a shortened stride length and an increased angle of placement of the hindfeet relative to artificially reared and suckle-control animals. The altered gait pattern may be the result of alcohol-induced hippocampal and cerebellar damage during the brain growth spurt.

Effects of postnatal ethanol exposure on glial cell development in rat optic nerve

This study morphologically evaluated the effects of limited postnatal alcohol exposure on the development of glial cells in the rat optic nerve. Rat pups were artificially reared on Days 5-18 with a supplemented milk diet fed via a chronic gastrostomy tube. Experimental animals received 4% ethanol in their diet on Days 5-9, otherwise the experimental and control animals received identical diets. Optic nerve tissues were prepared for electron microscopy on Days 10, 16, 22, 29, and 90. There were fewer glial cells per cross section and the cross-sectional areas of optic nerves were smaller on Days 10 and 16 in the ethanol-exposed animals. The alcohol caused a delay in the maturation of oligodendroglial cells at 10 days as evidenced by decreases in the total number of oligodendroglia present and by a delay in the appearance of immature cells within the oligodendroglial lineage. All of these effects were compensated for at later ages. There was no evidence of alcohol-induced degeneration of glial cells or their organelles. Thus, postnatal alcohol exposure causes a delay in oligodendrocyte maturation but appears to have no long-term effects on the glial cell population of rat optic nerve.

Neonatal ethanol exposure: functional alterations associated with cerebellar growth retardation

The effects of alcohol exposure during the brain growth spurt on development and on behavioral assessments of functional alterations in the cerebellum were examined in the rat. Rat pups were exposed via an artificial rearing technique to either a 2.50% w/v or 2.15% w/v EtOH-milk formula during a period encompassing the brain growth spurt. An artificially reared control group and a suckle control group were also included. Peak blood alcohol concentrations for animals in the high and low dose alcohol exposure groups were approximately 300 mg/dl and 180 mg/dl, respectively. Reductions in brain minus cerebellum to body weight (BR-C/BD) and cerebellum to body weight (C/BD) ratios were noted in animals from each of the alcohol-treated groups. Some catch-up growth in terms of brain mass was noted in animals from each of the alcohol-exposed groups. Animals exposed to alcohol during the neonatal period displayed deficits on several tests of balance and motor ability. Alcohol-exposed animals performed more poorly than controls when traversing two parallel horizontal rods and on tests of hindlimb and head elevation. No differences were noted in the ability to remain on a rotating drum. These results suggest that some of the behavioral consequences of neonatal ethanol exposure might be due to ethanol's actions on the cerebellum.

Differential neuronal loss following early postnatal alcohol exposure

Neonatal rats were exposed to 6.6 g/kg of alcohol each day between postnatal days 4 and 10 while artificial-rearing procedures were used, in a manner which produced high peak and low trough blood alcohol concentrations each day. Gastrostomy controls were reared artificially with maltose/dextrin isocalorically substituted for alcohol in the milk formula, and suckle controls were reared normally by dams. The pups were sacrificed on day 10 and tissue sections (2 microns thick) were obtained in the sagittal plane through the cerebellum and in the horizontal plane through the hippocampal formation. Overall area measures were obtained for the hippocampus proper, area dentata, and cerebellum, along with areas of the cell layers of these regions. In the hippocampal formation, cell counts were made of the pyramidal cells of the hippocampus proper, the multiple cell types of the hilus, and the granule cells of the area dentata. In the cerebellum, cell counts of Purkinje cells, granule cells of the granular layer, granule cells of the external granular layer, and mitotic cells of the external granular layer were obtained from lobules I, V, VII, VIII, and IX. Alcohol selectively reduced areas and neuronal numbers in the cerebellum but had no significant effects on neuronal numbers in the hippocampal formation. Purkinje cells exhibited the greatest percent reductions, and cerebellar granule cells were significantly reduced in the granular layer but not in the external granular layer. All lobules showed these effects, but lobule I was significantly more affected than the other four lobules that were analyzed. The results demonstrate the differential vulnerability of selected neuronal populations to the developmental toxicity of alcohol exposure during the brain growth spurt.

Prenatal brain malformations following acute ethanol exposure in the rat

Morphology of the cerebral cortex was studied in fetuses on gestational Day 21 following oral administration of several doses of ethanol (for total doses of 10, 15, or 18 g/kg) to pregnant rats on gestational Days 14 and 15, a critical period for the development of the cerebral cortex. All doses of ethanol were associated with a reduction in maternal weight gain, fetal body weight, and placental weight. Only the high dose of ethanol (total dose 18 g/kg) caused significant fetal cortical thinning. Acute exposure of pregnant rats to ethanol produced dose-dependent malformations of the cerebral cortex and hippocampus in fetuses. On gestational Day 21, the 18 g/kg group contained fetuses with severely disorganized cortical architecture, heterotopias of the cerebral cortex, pia and choroid plexus, and status verrucosus deformis. Fetuses from the 10 g/kg group had less severe malformations, such as disorganization of layers of cortical neurons and dentate granule cells while fetuses from the 15 g/kg group had a mixture of severe and minor malformations. This study demonstrates that acute ethanol exposure during a critical period of development in rats can result in brain malformations similar to those reported in human fetuses and neonates from alcoholic mothers.

Prenatal ethanol alters gait in rats

Rats exposed to ethanol in utero were assessed for changes in gait at 55 days of age. Ethanol-exposed animals had significantly shorter stride lengths, more open step angles, and less gait symmetry than control rats. There were no differences in stance width or apparent speed. This pattern of changes in motor function indicates that prenatal exposure to ethanol produces long-lasting "ataxia" in rats. These results closely resemble previous findings of altered gait following neonatal ethanol exposure in rats, as well as clinical findings in some FAS children. The results are consistent with an hypothesis of prenatal ethanol-induced disruption of functional hippocampal and/or cerebellar development. Ataxia and gait dysfunction may be sensitive indicators of ethanol teratogenesis.

Blood alcohol concentration and microencephaly: a dose-response study in the neonatal rat

The relationships among microencephaly, peak blood alcohol concentration (BAC), and dose of alcohol were examined in a rat model of third-trimester fetal alcohol effects. Ethyl alcohol was administered to neonatal rats from postnatal day 4 to day 10 during the brain growth spurt via an artificial rearing technique. Groups of rats received one of nine doses of alcohol (0.0, 2.5, 3.3, 4.0, 4.5, 5.3, 6.6, 7.5, or 8.5 g/kg body weight) administered in 8 hours each day. BACs were determined on postnatal days 6 and 7 at times corresponding to peak and trough BACs, respectively. On postnatal day 10, brains were removed, and total brain weights, cerebellar weights and brainstem weights were measured. Pups receiving 4.0 g/kg/day or less had mean peak BACs below 150 mg/dl and did not exhibit significant microencephaly when compared with controls. Higher dosages further increased the peak BAC and produced significant microencephaly. While a dose of 4.5 g/kg/day was sufficient to decrease significantly both total brain weight and cerebellar weight, a minimum dose of 6.6 g/kg/day was required for significant restriction of brainstem weight. The dose of 7.5 g/kg/day yielded a mean peak BAC of 420 mg/dl and reduced total brain weight, cerebellar weight, and brainstem weight by 33%, 52%, and 22%, respectively, relative to controls. Exposure to 8.5 g/kg/day was uniformly lethal. Peak BAC and total brain weight were highly correlated (r = -.916). As peak BAC increased, total brain weight decreased linearly. Comparisons with previous studies indicate that condensing the daily dose of alcohol effectively reduced the threshold doses for microencephaly and lethality.