Prenatal ethanol exposure permanently reduces the number of pyramidal neurons in rat hippocampus

Studies in animal models and humans suggesting a role of nerve growth factor in schizophrenia-like disorders

Neurotrophic factors, such as nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF), are known to play a crucial role in growth, differentiation and function in a variety of brain neurons during development and in adult life. We have recently shown that environmental changes, aggressive behavior and anxiety-like responses alter both circulating and brain basal NGF levels. In the present review, we present data obtained using animal models which suggest that neurotrophic factors, particularly NGF and BDNF, might be implicated in mechanism(s) leading to a condition associated with schizophrenic-like behaviors. The hypothesis that neurotrophins of the NGF family can be implicated in some maldevelopmental aspects of schizophrenia is supported by findings indicating that the constitutive levels of NGF and BDNF are affected in schizophrenic patients.

Ethanol-induced alterations in the expression of neurotrophic factors in the developing rat central nervous system

Neonatal rats were exposed to ethanol throughout gestation, or during the early postnatal period (postnatal days 4-10 (P4-10)), and enzyme-linked immunoabsorbent assays were subsequently conducted in order to assess nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) protein content in hippocampus, septum, cortex/striatum and cerebellum. These determinations revealed that following prenatal ethanol treatment, there were significant ethanol-induced increases in NGF in P1 cortex/striatum, but no changes in any of the three neurotrophic factors (NTFs) in the other brain regions. Cortex/striatal NGF protein returned to control levels by P10. Following early postnatal exposure, BDNF was elevated in hippocampus and cortex/striatum (assessed on P10), and NGF was also enhanced in cortex/striatum at this age. Hippocampal and cortex/striatal BDNF returned to control levels by P21, but cortex/striatal NGF levels remained enhanced at this age. This NTF did not differ in ethanol and control animals by P60, however. The possible significance of elevated levels of NTFs as a function of ethanol exposure is discussed, and it is speculated that while such alterations could play a protective role, increases in these substances during critical developmental periods could also prove to be deleterious, and could even contribute to certain of the neuropathologies which have been observed following developmental ethanol exposure.

Effect of neonatal ethanol exposure on parvalbumin-expressing GABAergic neurons of the rat medial septum and cingulate cortex

This study was performed to determine the long-term effects of ethanol exposure during the brain growth spurt (postnatal days 4-10) on the number of parvalbumin-immunoreactive (PA+) GABAergic neurons in the adult (P60) rat medial septum and anterior cingulate cortex. Significant loss of neurons within each of these populations has previously been demonstrated following prenatal ethanol exposure. In the present study, no significant differences in the number of PA+ neurons were found in either the medial septum or the cingulate cortex when control and ethanol-exposed animals were compared. The cellular densities and volumetric measures in both brain regions were also similar in the two groups. We speculate that compensatory up-regulative mechanisms may have accounted for the protection of the PA neuronal populations in these two areas following the early neonatal exposure.

Effects of chronic prenatal ethanol exposure on hippocampal glutamate release in the postnatal guinea pig

This study was designed to test the hypothesis that chronic prenatal ethanol exposure decreases basal and stimulated L-glutamate release in the hippocampus of young, postnatal guinea pigs. Timed, pregnant guinea pigs were randomly assigned to one of the following three chronic treatment groups: 4 g ethanol/kg maternal body weight/day, isocaloric-sucrose and pair-feeding to the ethanol group, and water. Each oral treatment was given daily throughout gestation. Spontaneous locomotor activity was increased on postnatal day (PD) 10, and brain and hippocampal weights were decreased on PD 12 in the offspring of the ethanol group compared with the isocaloric-sucrose/pair-fed and water groups. On PD 12, the 45 mM K(+)- and 10 microM veratridine-stimulated release of glutamate in transverse hippocampal slices was decreased in the ethanol group compared with the two control groups. This alteration in glutamate release produced by chronic prenatal ethanol exposure may decrease the efficiency of excitatory synaptic transmission in the hippocampus during postnatal life.

Effects of prenatal alcohol exposure on the hippocampus: spatial behavior, electrophysiology, and neuroanatomy

Prenatal exposure to alcohol can result in fetal alcohol syndrome (FAS), characterized by growth retardation, facial dysmorphologies, and a host of neurobehavioral impairments. Neurobehavioral effects in FAS, and in alcohol-related neurodevelopmental disorder, include poor learning and memory, attentional deficits, and motor dysfunction. Many of these behavioral deficits can be modeled in rodents. This paper reviews the literature suggesting that many fetal alcohol effects result, at least in part, from teratogenic effects of alcohol on the hippocampus. Neurobehavioral studies show that animals exposed prenatally to alcohol are impaired in many of the same spatial learning and memory tasks sensitive to hippocampal damage, including T-mazes, the Morris water maze, and the radial arm maze. Direct evidence for hippocampal involvement is provided by neuroanatomical studies of the hippocampus documenting reduced numbers of neurons, lower dendritic spine density on pyramidal neurons, and decreased morphological plasticity after environmental enrichment in rats exposed prenatally to alcohol. Electrophysiological studies also demonstrate changes in synaptic activity in in vitro hippocampal brain slices isolated from prenatal alcohol-exposed animals. Considered together, these observations demonstrate that prenatal exposure to alcohol can result in abnormal hippocampal development and function. Such studies provide a better understanding of neurological deficits associated with FAS in humans, and may also contribute to the development of strategies to ameliorate the effects of prenatal alcohol exposure on behavior.

Ethanol inhibits development of dendrites and synapses in rat hippocampal pyramidal neuron cultures

Evidence suggests that some neuropathologic manifestations of Fetal Alcohol Syndrome (FAS) result from the disruption of neuromorphogenesis and synapse formation in the hippocampus. Prior research in this laboratory has shown that ethanol in the medium during the first 24 h in culture increases the number of minor processes (the precursors of axons and dendrites) and accelerates the rate at which axons are formed in low-density cultures of embryonic rat hippocampal neurons. The current study examined the effects of ethanol on the subsequent development of dendrites and synapses in these cultures. Quantitative morphometric analysis utilized double-immunofluorescent staining for MAP2 and synapsin I to visualize dendrites and synaptic specializations, respectively. Six days of ethanol (200, 400 or 600 mg/dl) in the medium, beginning at the time of plating, resulted in decreases in total dendritic length per cell, dendrite number per cell, length of individual dendrites and synapse number per innervated dendrite but had no effect on cell survival. The decrease in synapse number was correlated with dendrite length, suggesting that ethanol's effects on synapse number are secondary to its effects on dendritogenesis. Taken together with our previous findings, these results are the first to demonstrate that ethanol has differential effects on axonal and dendritic growth in a culture model of neurons that are vulnerable to ethanol-induced cytoarchitectural abnormalities during development in vivo.

Effects of chronic prenatal ethanol exposure on locomotor activity, and hippocampal weight, neurons, and nitric oxide synthase activity of the young postnatal guinea pig

Decreased nitric oxide synthase (NOS)-catalyzed formation of NO from L-arginine may be involved in ethanol teratogenesis involving the hippocampus. This hypothesis was tested by determining the effects of chronic prenatal ethanol exposure on locomotor activity and on hippocampal weight, number of CA1 and CA3 pyramidal cells and dentate gyrus granule cells, and NOS activity of the postnatal guinea pig. Timed, pregnant guinea pigs received one of the following chronic oral regimens throughout gestation: 4 g ethanol/kg maternal body weight/day, isocaloric-sucrose/pair-feeding, or water. At postnatal day (PD) 10, spontaneous locomotor activity was measured. At PD 12, histological analysis was performed on the hippocampal formation, in which hippocampal CA1 and CA3 pyramidal cells and dentate gyrus granule cells were counted; body, brain, and hippocampal weights were measured; and hippocampal NOS enzymatic activity was determined using a radiometric assay. Chronic prenatal ethanol exposure produced hyperactivity, decreased the brain and hippocampal weights with no change in body weight, decreased the number of hippocampal CA1 pyramidal cells by 25-30%, and had no effect on hippocampal NOS activity compared with the two control groups. These data, together with our previous findings in the fetal guinea pig, demonstrate that chronic prenatal ethanol exposure decreases hippocampal NOS activity in near-term fetal life that temporally precedes the selective loss of hippocampal CA1 pyramidal cells in postnatal life.

Fetal alcohol exposure alters serotonin transporter sites in rat brain

This study examined the effects of fetal alcohol exposure (FAE) on serotonin transporter (5-HTT) binding sites in the brains of developing male and female rat offspring using the technique of quantitative autoradiography. Time-pregnant dams were fed liquid ethanol diet, isocaloric diet without ethanol or normal rat chow. Male and female offspring were sacrificed at 21, 40 and 60 days of age, brains removed and sectioned for analysis of 5-HTT sites. FAE led to distinct effects on 5-HTT sites depending on the age and gender of the offspring. FAE increased 5-HTT binding sites in cortical layers 5, 6, hippocampal layers CA(2,3), lateral nucleus of the amygdala and in the dorsal raphe nucleus. FAE decreased 5-HTT binding sites in the medial nucleus of amygdala, dorsomedial and ventromedial nuclei of the hypothalamus. FAE decreased 5-HTT binding sites temporarily in the ventromedial nucleus of the hypothalamus in the 21-day-old female; this effect was found to disappear by day 40. In contrast, FAE increased 5-HTT sites in the lateral nucleus of the amygdala in the adult animal, suggesting that ethanol exposure in utero may alter serotonin neurotransmission in discrete brain regions permanently.

Glial-derived neurotrophic factor (GDNF) prevents ethanol-induced apoptosis and JUN kinase phosphorylation

Ethanol exposure during neural development leads to substantial neuronal loss in multiple brain regions. Our previous research indicated that exogenous glial-derived neurotrophic factor (GDNF) attenuated ethanol-induced cerebellar Purkinje cell loss. Additionally, ethanol decreased GDNF release suggesting that ethanol disrupts GDNF-signaling pathways. The present experiments utilized a homogeneous GDNF-responsive neuroblastoma cell line (SK-N-SH) to test the hypothesis that exogenous GDNF could attenuate ethanol-induced cell loss by suppressing cytotoxic signaling pathways and cell suicide. We measured two independently regulated markers of apoptosis, DNA fragmentation and the externalization of phosphatidylserine to the outer cell membrane leaflet. Ethanol induced a dose-related increase in both apoptosis and necrosis. Lower concentrations of ethanol (34 and 68 mM) specifically increased DNA fragmentation, while all concentrations (up to 137 mM) increased phosphatidylserine translocation, suggesting that ethanol induction of apoptosis is not a unitary process. Furthermore, only higher concentrations of ethanol (103 and 137 mM) induced necrosis. Additionally, ethanol specifically induced phosphorylation of c-jun N-terminal-kinase (JNK), a mitogen-activated protein (MAP) kinase selectively associated with apoptosis. In contrast, ethanol did not alter the phosphorylation of another MAP kinase, the extracellular signal-regulated kinases (ERK) that mediate cell survival. Thus, ethanol activated specific intracellular cell death-associated pathways and induced cell death. GDNF, in turn, prevented both ethanol-induced apoptosis and the activation of the death-associated JNK cascade. Therefore, GDNF may regulate multiple pathways to prevent ethanol-induced cell loss.

Amelioration of fetal alcohol-related neurodevelopmental disorders in rats: exploring pharmacological and environmental treatments

Fetal alcohol syndrome (FAS) and alcohol-related neurodevelopmental disorders (ARNDs) in children are characterized by life-long compromises in learning, memory, and adaptive responses. Until the advent of effective prevention measures, it will remain necessary to seek ways to treat the life-long neurobehavioral consequences of prenatal alcohol exposure. To date, there are no clinical remedies to recommend for either specific or global fetal alcohol effects. This article reviews our basic research in animal models that assesses the potential of global environmental manipulations or specific psychopharmacological treatments to ameliorate the neurobehavioral effects of prenatal exposure to alcohol. Postweaning environmental enrichment can improve behavioral performance and ameliorate or even eliminate deficits in prenatal alcohol-exposed rats, although there is persistent impairment in neuronal plasticity, as indicated by the failure of hippocampal pyramidal cells to increase dendrite spine density. Behavioral and neural responses to CNS stimulants differ in rats exposed prenatally to alcohol, although it is not clear that these shifts in dose-response curves would predict benefit to children. Although the present results may sound a note of optimism for the development of effective treatment strategies for children with FAS or ARNDs, it is important to consider that application of these findings in rodents may not be straightforward. We also need to know the critical features of specific environments that influence brain development, and the limits of pharmacotherapy, as well as critical periods of exposure. Continued study of the beneficial, ameliorative effects of environmental enrichment, rehabilitative training, and of pharmacological therapies in animal models, will remain a valuable source of information for eventually devising treatments specific for children with FAS and ARNDs.

Comparative effects of developmental thiamine deficiencies and ethanol exposure on the morphometry of the CA3 pyramidal cells

Maternal alcoholism and thiamine deficiency are frequently considered to be the causal agents of the central nervous system (CNS) damage associated with mental retardation in the offspring. For further understanding of pathological mechanisms underlying CNS damage in both disorders, histological studies were undertaken in developing rats to compare the hippocampus CA3 pyramidal cells measurements and density between three patterns of thiamine deficiency and chronic alcohol exposure. Female rats were given thiamine-deficient diet during different periods of gestation and lactation to obtain pre-, peri-, and postnatal thiamine-deficient pups. Twelve percent ethanol/water drinking fluid was given to mothers throughout gestation and lactation to obtain ethanol-exposed pups. Thiamine was administered during developmental ethanol exposure to assess the extent of interference between ethanol and thiamine metabolism. Nondrug-treated dams were allowed ad lib access to food and water during gestation and lactation to yield control pups. Hippocampus histology was performed in 45-day-old rats, and the CA3 pyramidal cells measurements and density assessed and compared between all treatment groups. It appears that the mean nuclear size of pyramidal cells in the field CA3 was significantly reduced in all the treatments compared to the control. While the mean nuclear size decreased more severely in development ethanol exposure than in the three patterns of thiamine deficiency, no significant difference was noted when pre-, peri-, and postnatal thiamine-deficient rats were compared. However, thiamine administration during developmental ethanol exposure partially restored the mean nuclear size. In contrast, comparisons between ethanol-exposed pups and the three patterns of thiamine-deficient pups, exhibited similar intensity in the deficit of CA3 pyramidal cells. Cell loss generated by ethanol treatment was not suppressed by thiamine administration. Common and separate mechanisms underlying the effects of alcohol intoxication and thiamine deficiency on cell death and cell atrophy were suggested.

Prenatal ethanol effects on NGF level, NPY and ChAT immunoreactivity in mouse entorhinal cortex: a preliminary study

It has been reported that maternal ethanol consumption leads to deficits in the limbic areas involved in cognitive functions and interferes with synthesis and utilization of neurotrophins. In the present study, it was hypothesized that prenatal alcohol intake might induce neuroanatomical alterations in the entorhinal cortex (EC). We also investigated the possible EC involvement of brain nerve growth factor (NGF), the first neurotrophin to be isolated, during such pathological events. To test this hypothesis, we used pregnant mice exposed to ethanol during EC neurogenesis (starting about gestational day 8). Our data show that prenatal alcohol intake in male mice alters the EC neuronal growth and differentiation. These morphological alterations are accompanied by an altered NGF level in the EC of prenatal alcohol-treated mice. We also found a decrease in choline acetyltransferase- and neuropeptide Y-immunopositive neurons in the EC of alcohol-exposed mice. However, the relationship between neuronal damage induced in the EC by ethanol, low presence of NGF, and the possible functional and behavioral consequences remains to be elucidated.

Abnormalities in neuronal process extension, hippocampal development, and the ventricular system of L1 knockout mice

In humans, mutations in the L1 cell adhesion molecule are associated with a neurological syndrome termed CRASH, which includes corpus callosum agenesis, mental retardation, adducted thumbs, spasticity, and hydrocephalus. A mouse model with a null mutation in the L1 gene (Cohen et al., 1997) was analyzed for brain abnormalities by Nissl and Golgi staining and immunocytochemistry. In the motor, somatosensory, and visual cortex, many pyramidal neurons in layer V exhibited undulating apical dendrites that did not reach layer I. The hippocampus of L1 mutant mice was smaller than normal, with fewer pyramidal and granule cells. The corpus callosum of L1-minus mice was reduced in size because of the failure of many callosal axons to cross the midline. Enlarged ventricles and septal abnormalities were also features of the mutant mouse brain. Immunoperoxidase staining showed that L1 was abundant in developing neurons at embryonic day 18 (E18) in wild-type cerebral cortex, hippocampus, and corpus callosum and then declined to low levels with maturation. In the E18 cortex, L1 colocalized with microtubule-associated protein 2, a marker of dendrites and somata. These new findings suggest new roles for L1 in the mechanism of cortical dendrite differentiation, as well as in guidance of callosal axons and regulation of hippocampal development. The phenotype of the L1 mutant mouse indicates that it is a potentially valuable model for the human CRASH syndrome.

Effect of chronic prenatal ethanol exposure on nitric oxide synthase I and III proteins in the hippocampus of the near-term fetal guinea pig

Chronic prenatal ethanol exposure suppresses nitric oxide synthase (NOS) enzymatic activity, in the hippocampus of the near-term fetal guinea pig at gestational day (GD) 62. The objective of this study was to determine if this decrease in NOS activity is the result of decreased NOS I and NOS III protein expression. Pregnant guinea pigs received oral administration of 4 g ethanol/kg maternal body weight/day (n = 8), isocaloric-sucrose/pair feeding (n = 8), or water (n = 8) from GD 2 to GD 61. The NOS I and NOS III protein expression and localization in the hippocampus were determined using Western blot analysis and immunohistochemistry, respectively. The chronic ethanol regimen produced fetal body, brain, and hippocampal growth restriction compared with the isocaloric-sucrose/pair fed and water groups but did not affect the expression or localization of NOS I and NOS III proteins in the hippocampus. The decrease in NOS enzymatic activity induced by chronic prenatal ethanol exposure may be the result of posttranslational modification of NOS I and/or NOS III protein in the hippocampus of the near-term fetal guinea pig.

The effect of the timing of ethanol exposure during early postnatal life on total number of Purkinje cells in rat cerebellum

We have previously shown that exposing rats to a high dose of ethanol on postnatal d 5 can affect Purkinje cell numbers in the cerebellum whilst similar exposure on d 10 had no such effect. The question arose whether a longer period of ethanol exposure after d 10 could produce loss of Purkinje cells. We have examined this question by exposing young rats to a relatively high dose (approximately 420-430 mg/dl) of ethanol for 6 d periods between the ages of either 4 and 9 d or 10 and 15 d of age. Exposure was carried out by placing the rats in an ethanol vapour chamber for 3 h per day during the exposure period. Groups of ethanol-treated (ET), separation controls (SC) and mother-reared controls (MRC) were anaesthetised and killed when aged 30 d by perfusion with buffered 2.5% glutaraldehyde. Stereological methods were used to determine the numbers of Purkinje cells in the cerebellum of each rat. MRC, SC and rats treated with ethanol between 10-15 d of age each had, on average, about 254-258 thousand cerebellar Purkinje cells; the differences between these various groups were not statistically significant. However, the rats treated with ethanol vapour between 4-9 d of age had an average of only about 128000+/-20000 Purkinje cells per cerebellum. This value was significantly different from both the MRC and group-matched SC animals. It is concluded that the period between 4 and 9 d of age is an extremely vulnerable period during which the rat cerebellar Purkinje cells are particularly susceptible to the effects of a high dose of ethanol. However, a similar level and duration of ethanol exposure commencing after 10 d of age has no significant effect on Purkinje cell numbers.

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.

Electrophysiology of hippocampal CA1 neurons after prenatal ethanol exposure

In the present study, we examined the longitudinal effects of prenatal ethanol exposure on the electrophysiological characteristics of CA1 neurons in hippocampal slices. Hippocampal slices were obtained from young (25-32-day old) and adult (63-77-day old) male offspring of rats given one of four treatments during gestation. Three groups of pregnant rats were orally intubated with 0, 4, or 6 g/kg ethanol on gestational days 8-20. Caloric intake for the 0- (nutritional control) and 4-g/kg groups was yoked to that of the 6 g/kg group. A fourth group (untreated control) was not intubated, and was given ad lib access to food. Long-term potentiation and paired-pulse inhibition were unaffected by prenatal ethanol exposure in young and adult rats; however, slices taken from the young 6 g/kg ethanol group displayed a significantly lower maximal CA1 population spike amplitude evoked by Schaffer collateral stimulation as compared to young controls. This difference was not observed in adult animals. These data suggest that some aspects of hippocampal physiology are negatively affected in young rats as a result of prenatal ethanol exposure, but this effect reverses as the animal matures.

Bcl-2 overexpression protects the neonatal cerebellum from ethanol neurotoxicity

The developing nervous system is extremely sensitive to ethanol, and exposure often produces a condition known as the fetal alcohol syndrome. Although mechanisms underlying developmental ethanol toxicity have long been sought, they remain poorly understood. In this study, we examined the ability of the cell death repressor gene bcl-2 to protect against ethanol neurotoxicity. Transgenic mice overexpressing bcl-2 in neurons were exposed to ethanol vapor on postnatal days 4 and 5, which is the peak period of vulnerability of cerebellar Purkinje cells to ethanol. While exposure of wild-type animals to ethanol resulted in significant loss of Purkinje cells by P5, similar exposure of homozygous and heterozygous transgenics had no effect on the number of these neurons. This study suggests that bcl-2 can protect neurons from ethanol neurotoxicity and that modulation of cell death effector or repressor gene products may play a significant role in developmental ethanol neurotoxicity.

Neurotrophic factors BDNF and GDNF protect embryonic chick spinal cord motoneurons from ethanol neurotoxicity in vivo

Maternal consumption of ethanol is widely recognized as a leading cause of mental and physical deficits. Many populations of the central nervous system are affected by the teratogenic effects of ethanol. Neurotrophic factors (NTFs) have been shown to protect against ethanol neurotoxicity in culture, although there have been no demonstrations of such protection in vivo, in specific neuronal populations. Previous studies have demonstrated that ethanol is toxic to developing chick embryo motoneurons when administered from embryonic day 10 (E10) to E15. NTFs such as brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF) have been shown to support developing spinal cord motoneurons, and when exogenously applied, decrease naturally occurring cell death, and protect against axotomy. The concurrent delivery of BDNF or GDNF with ethanol to the embryonic chick from E10 to E15 was designed to examine the capacity of these NTFs to provide in vivo neuroprotection for this ethanol-sensitive motoneuron population. Analysis of motoneuron numbers indicated that both BDNF and GDNF provided protection to developing spinal cord motoneurons from ethanol toxicity, restoring motoneuron numbers to control levels. This study represents the first demonstration of in vivo neuroprotection from ethanol toxicity with respect to specific neuronal populations.

Effects of moderate alcohol consumption on the central nervous system

The concept of moderate consumption of ethanol (beverage alcohol) has evolved over time from considering this level of intake to be nonintoxicating and noninjurious, to encompassing levels defined as "statistically" normal in particular populations, and the public health-driven concepts that define moderate drinking as the level corresponding to the lowest overall rate of morbidity or mortality in a population. The various approaches to defining moderate consumption of ethanol provide for a range of intakes that can result in blood ethanol concentrations ranging from 5 to 6 mg/dl, to levels of over 90 mg/dl (i.e., approximately 20 mM). This review summarizes available information regarding the effects of moderate consumption of ethanol on the adult and the developing nervous systems. The metabolism of ethanol in the human is reviewed to allow for proper appreciation of the important variables that interact to influence the level of exposure of the brain to ethanol once ethanol is orally consumed. At the neurochemical level, the moderate consumption of ethanol selectively affects the function of GABA, glutamatergic, serotonergic, dopaminergic, cholinergic, and opioid neuronal systems. Ethanol can affect these systems directly, and/or the interactions between and among these systems become important in the expression of ethanol's actions. The behavioral consequences of ethanol's actions on brain neurochemistry, and the neurochemical effects themselves, are very much dose- and time-related, and the collage of ethanol's actions can change significantly even on the rising and falling phases of the blood ethanol curve. The behavioral effects of moderate ethanol intake can encompass events that the human or other animal can perceive as reinforcing through either positive (e.g., pleasurable, activating) or negative (e.g., anxiolysis, stress reduction) reinforcement mechanisms. Genetic factors and gender play an important role in the metabolism and behavioral actions of ethanol, and doses of ethanol producing pleasurable feelings, activation, and reduction of anxiety in some humans/animals can have aversive, sedative, or no effect in others. Research on the cognitive effects of acute and chronic moderate intake of ethanol is reviewed, and although a number of studies have noted a measurable diminution in neuropsychologic parameters in habitual consumers of moderate amounts of ethanol, others have not found such changes. Recent studies have also noted some positive effects of moderate ethanol consumption on cognitive performance in the aging human. The moderate consumption of ethanol by pregnant women can have significant consequences on the developing nervous system of the fetus. Consumption of ethanol during pregnancy at levels considered to be in the moderate range can generate fetal alcohol effects (behavioral, cognitive anomalies) in the offspring. A number of factors--including gestational period, the periodicity of the mother's drinking, genetic factors, etc.--play important roles in determining the effect of ethanol on the developing central nervous system. A series of recommendations for future research endeavors, at all levels, is included with this review as part of the assessment of the effects of moderate ethanol consumption on the central nervous system.

Effect of ethanol on neurotrophin-mediated cell survival and receptor expression in cultures of cortical neurons

The interaction of ethanol and neurotrophin-mediated cell survival was examined in primary cultures of cortical neurons. Cells were obtained from rat fetuses on gestational day 16 and maintained in a medium supplemented with either 10% or 1.0% fetal calf serum (FCS). Exogenous nerve growth factor (NGF; 20 ng/ml), brain-derived neurotrophic factor (BDNF; 20 ng/ml) or neurotrophin 3 (NT-3; 20 ng/ml) was added to the cultures alone, or in combination with ethanol (400 mg/dl). The number of viable neurons was determined after a 48 h treatment with a growth factor and/or ethanol. The effects of ethanol on the expression of high affinity neurotrophin receptors (trkA, trkB, and trkC) and the low-affinity receptor (p75), were analyzed using Western immunoblots. In untreated cultures, 22.7% and 26.3% of the cells raised in a medium containing 10% and 1.0% FCS, respectively, were lost. Only NGF prevented the death of the cultured cortical neurons. Ethanol was toxic; it caused a 23.5% and 16.7% loss of cells (for cells grown in a medium containing 10% and 1.0% FCS, respectively) beyond that occurring 'naturally' in an untreated culture. Ethanol completely blocked the NGF-mediated cell survival. In general, BDNF and NT-3 did not offset the toxic effect of ethanol. Immunoblotting studies showed that the expression of p75 was significantly (p < 0.05) lower (40%) in ethanol-treated cultures, but ethanol did not affect trk expression. Thus, ethanol has specific effects upon NGF-mediated cell survival and the effects on the low affinity receptor imply that p75 specifically plays an important role in NGF signaling.

Prenatal ethanol exposure reduces parvalbumin-immunoreactive GABAergic neuronal number in the adult rat cingulate cortex

The effect of prenatal ethanol exposure on the number of parvalbumin-immunoreactive (PA+) GABAergic neurons in the adult rat anterior cingulate cortex was determined. Pregnant Long-Evans rats were maintained on one of three diets throughout gestation: an ethanol-containing liquid diet, a similar, control liquid diet with the isocaloric substitution of sucrose for ethanol, or a lab chow control diet. Offspring were euthanized on postnatal day 60 and brains were prepared for parvalbumin immunocytochemistry. Rats exposed to the ethanol-containing diet contained 45% fewer PA+ neurons in the anterior cingulate cortex compared with sucrose and chow controls. This reduction occurred in the absence of changes in structure volume, and occurred in the absence of changes in PA+ neuronal size.

Neuroanatomical and neurophysiological mechanisms involved in central nervous system dysfunctions induced by prenatal alcohol exposure

One of the most severe consequences of maternal ethanol consumption is the damage to the developing central nervous system, which is manifested by long-term cognitive and behavioral deficits in the offspring. Prenatal exposure to ethanol affects many crucial neurochemical and cellular components of the developing brain. Ethanol interferes with all of the stages of brain development, and the severity of the damage depends on the amount of ethanol intake and level of exposure. Experimental observations also indicate that the toxic effects of ethanol are not uniform: some brain regions are more affected than others and, even within a given region, some cell populations are more vulnerable than others. The neocortex, the hippocampus, and the cerebellum are the regions in which the neurotoxic effects of ethanol have been associated with the behavioral deficits. At the cellular level, ethanol disrupts basic developmental processes, including interference with division and proliferation, cell growth, and differentiation and the migration of maturing cells. Alterations in astroglia development and in neuronal-glial interactions may also influence the development of the nervous system. An impairment of several neurotransmitter systems and/or their receptors, as well as changes in the endocrine environment during brain development, are also important factors involved in the behavioral dysfunctions observed after prenatal ethanol exposure. Finally, some molecular mechanisms of ethanol-induced behavioral dysfunctions will be discussed.

Prenatal exposure to ethanol disrupts spatial memory: effect of the training-testing delay period

The present study investigated how variations in the period of delay between training and testing in the Morris water maze task affect the use of spatial memory in adult rats that were prenatally exposed to ethanol. Previous results utilizing the Morris water maze task have shown that prenatal, or early postnatal, exposure to ethanol produces deficits in the use of spatial memory, a type of memory that is dependent on an intact hippocampus. However, in these prior studies the delay period between the training of animals and the testing of spatial memory is typically fixed at only 1 day. In the current study, which utilized a revised training procedure within the Morris water maze task, the period of delay between training and testing was altered such that it was either 1 day or 3 days. Following the 3-day delay, different levels of prenatal exposure to ethanol impaired the use of spatial memory. In contrast, following the 1-day delay, prenatal exposure to ethanol failed to impair the use of spatial memory. The present study thus shows that prenatal exposure to ethanol differentially affects spatial memory in the Morris water maze task depending on the period of delay between training and testing.

Hippocampal nitric oxide synthase in the fetal guinea pig: effects of chronic prenatal ethanol exposure

The effects of chronic maternal administration of ethanol on nitric oxide synthase (NOS) activity and the numbers of NOS containing neurons, and CA1 and CA3 pyramidal neurons in the hippocampus of the near term fetal guinea pig at gestational day (GD) 62 were investigated. Pregnant guinea pigs received oral administration of 4 g ethanol/kg maternal body weight (n = 5), isocaloric sucrose/pair feeding (n = 5) or water (n = 5), or no treatment (NT; n = 5) from GD 2 to GD 61. NOS activity in the 25,000 x g supernatant of hippocampal homogenate was determined using a radiometric assay. The numbers of NOS containing neurons, and CA1 and CA3 pyramidal neurons were determined using NADPH diaphorase histochemistry and cresyl violet staining, respectively. The chronic ethanol regimen produced a maternal blood ethanol concentration of 193 +/- 13 mg/dl at 1 h after the second divided dose on GD 57. Chronic ethanol exposure produced fetal body, brain, and hippocampal growth restriction and decreased fetal hippocampal NOS activity compared with the isocaloric sucrose/pair feeding, water, and NT experimental groups, but did not affect the number of NOS containing and CA1 or CA3 pyramidal neurons. These data demonstrate that, in the near term fetus, chronic maternal administration of ethanol suppresses hippocampal NOS activity and consequent formation of NO, without loss of NOS containing neurons and prior to loss of CA1 pyramidal neurons that occurs in the adult.

A comparative study of ethanol, hypoglycemia, hypoxia and neurotrophic factor interactions with fetal rat hippocampal neurons: a multi-factor in vitro model developmental ethanol effects

Fetal alcohol syndrome (FAS) is characterized by numerous central nervous system anomalies, with the hippocampus being particularly vulnerable to developmental ethanol exposure. In addition to direct ethanol neurotoxicity, other conditions resulting from maternal ethanol consumption, such as hypoglycemia and hypoxia, may also contribute to FAS. The present study used a tissue culture system to model multiple conditions which may relate to in vivo FAS, and assessed their relative neurotoxicity with MTT assays. Gestational day 18 rat hippocampal cultures were exposed to varying ethanol concentrations, glucose withdrawal-induced hypoglycemic (gwHG, 16 h) or acute hypoxic (aHP, 2 h) conditions alone, as well as to co-treatments with ethanol and gwHG or aHP. Brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) have previously been shown to ameliorate ethanol-, hypoglycemia- and hypoxia-induced neurotoxicity. Therefore, their neuroprotective potential, along with ciliary neurotrophic factor (CNTF), was examined. Neuronal viability was reduced dose-dependently by ethanol, alone or with hypoglycemia or hypoxia. Ethanol + gwHG or aHP was not uniformly additive. NGF treatment provided the most extensive neuroprotection, being effective against ethanol (200 and 400 mg/dl), gwHG, and aHP, alone and combined. BDNF afforded similar protection, but not against ethanol + gwHG. CNTF protected only against aHP. CNTF + BDNF, previously shown to act synergistically, protected against ethanol + aHP up to 800 mg/dl ethanol, but not, paradoxically, against ethanol alone, gwHG, or ethanol + gwHG, all conditions BDNF alone protected against. This study demonstrated that several neurotrophic factors are capable of mitigating neurotoxicity associated with ethanol, hypoglycemia and hypoxia.

Spatial learning ability of rats following differing levels of exposure to alcohol during early postnatal life

Rats exposed to a relatively high dose (7.5 g/kg body weight) of alcohol on either the fifth or tenth postnatal day of age have been reported to have long-lasting deficits in spatial learning ability as tested on the Morris water maze task. The question arises concerning the level of alcohol required to achieve this effect. Wistar rats were exposed to either 2, 4 or 6 g/kg body weight of ethanol administered as a 10% solution. This ethanol was given over an 8-h period on the fifth postnatal day of age by means of an intragastric cannula. Gastrostomy controls received a 5% sucrose solution substituted isocalorically for the ethanol. Another set of pups raised by their mother were used as suckle controls. All surgical procedures were carried out under halothane vapour anaesthesia. After the artificial feeding regimes all pups were returned to lactating dams and weaned at 21 days of age. The spatial learning ability of these rats was tested in the Morris water maze when they were between 61-64 days of age. This task requires the rats to swim in a pool containing water made opaque and locate and climb onto a submerged platform. The time taken to accomplish this is known as the escape latency. Each rat was subjected to 24 trials over 3 days of the test period. Statistical analysis of the escape latency data revealed that the rats given 6 g/kg body weight of ethanol had significant deficits in their spatial learning ability compared with their control groups. However, there was no significant difference in spatial learning ability for the rats given either 2 or 4 g/kg body weight of ethanol compared with their respective gastrostomy or suckle control animals. We concluded that ethanol exposure greater than 4 g/kg over an 8-h period to 5-day-old rats is required for them to develop long-term deficits in spatial learning behaviour.

Basic fibroblast growth factor- and platelet-derived growth factor-mediated cell proliferation in B104 neuroblastoma cells: effect of ethanol on cell cycle kinetics

In vivo studies show (a) that early exposure to ethanol depletes neurons in the central nervous system (CNS) and (b) that a primary target of ethanol in the developing nervous system is proliferating neuronal precursors. We used a neuronal cell line (B 104 neuroblastoma cells) as an in vitro model for the effects of ethanol on the proliferation of neuronal precursors to test the hypothesis that ethanol interferes with growth factor-regulated proliferation of neuron-like precursors. The effects of ethanol on the mitogenic activity of two growth factors, basic fibroblast growth factor (bFGF) and platelet-derived growth factor AA and BB (PDGF-AA and PDGF-BB), were examined. Cell proliferation was monitored by tracing the change in the numbers of cultured cells over 4-5 days and in the cell cycle kinetics was determined using a cumulative labeling technique with bromodeoxyuridine (BrdU). Western immunoblots and immunohistochemical preparations show that B104 cells expressed the high affinity receptors for bFGF, PDGF-AA and PDGF-BB. The three growth factors were potent mitogens for the B104 cells; they promoted an increase in cell number even when the cells were grown in serum-free medium. Ethanol depressed the bFGF-, PDGF-AA- and PDGF-BB-mediated cell proliferation without altering the incidence of cell death. These changes in proliferation were concentration-dependent; at a concentration of 100 mg/dl, ethanol partially, but significantly inhibited growth factor-stimulated proliferation and higher ethanol concentrations (400 mg/dl or more) completely abolished growth factor-regulated cell proliferation. The effects of ethanol on cell growth were a result of ethanol-induced changes in growth factor-regulated cell cycle kinetics, principally the total length of the cell cycle and the fraction of the population that was actively cycling (the growth fraction). Ethanol completely negated the action of bFGF, but only partially blocked PDGF-promoted cycling activity. Thus, B104 cells are a suitable model for studying the effects of ethanol on neuronal proliferation. The blockage of bFGF- and PDGF-mediated cell proliferation by ethanol supports the hypothesis that growth factors are a target of ethanol neurotoxicity. Furthermore, the differential actions and effects of ethanol on the two growth factors mirror effects observed in vivo.

Moderate Alcohol Consumption and Psychological Stress during Pregnancy Induce Attention and Neuromotor Impairments in Primate Infants

This study examined the effect of moderate alcohol and/or psychological stress during prenancy on off-spring growth and behavior in 33 rhesus monkey infants (Macaca mulatta). Infants were derived from 1 of 3 groups of female: (1) alcohol-consuming,0.6g/Kg, Daily throughou gestation (equivalet, to 1-2 drinks), beginning 5 day prior to breeding;(2) alcohol-consuming (as above) and exposed to mild psychological stress(removal from home cage and exposed to 3 random noise bursts); (3) sucrose-consuming, equivolemic, and equicaloric to the alcohol solution.Beginning on day 4 postpartum, intantrs underwent brief weekly separations from their mother for assessment of growth, behavior, and facial dimensions. Results indicated that moderate alcohol consumption throughout pregnancy was sufficient to affect attention and neuromotor functioning, even though the infants were normol in birthweight, gestational length, and facial dimensions, Moreover, alcohol-induced neuromotor impairments were exacerbated by maternal exposure to psychological stress, and males from the alcohol/stress condition had reduced birthweights. Finally, although all females consuming alcohol produced viable offspring, alcohol accompanie by stress during gestation resulted in 23% fetal losses (abortion and stillbirths).

Effects of ethanol on the inner layers of chick retina during development

Optic nerve hypoplasia is an important malformation of the fetal alcohol syndrome whose teratogenic mechanisms are unknown. In our experimental model we have quantified the concentration of ethanol and acetaldehyde in the retina and vitreous humor of the developing chick. The effect of ethanol alone during retinal development was analyzed by conventional histological techniques and by immunostaining. A single injection of ethanol in the vitelline sac at the beginning of retinal cell differentiation retarded synaptogenesis in the inner plexiform layer and produced abundant ganglion cell death and a sharp diminution of myelinic axons. Our observations could help to explain certain alterations described in children exposed to ethanol during the development of their nervous system.

Ethanol influences on the chick embryo spinal cord motor system. II. Effects of neuromuscular blockade and period of exposure

The study described below was performed as a continuation of a previous study in which we found reduced motoneuron number in lumbar spinal cord of the chick embryo following chronic ethanol administration from embryonic day 4 (E4) to E11. We sought to determine whether this reduction was due to primary ethanol toxicity or to enhancement of naturally occurring cell death (NOCD) and to determine whether administration of ethanol at a later period of development could also reduce motoneuron number. Earlier studies have shown that curare suspends NOCD in the chick embryo. By administering both ethanol and curare to these embryos from E4 to E11 and examining the lumbar spinal cord on E12, we determined that ethanol was directly toxic to motoneurons and reduced motoneuron number in the absence of NOCD. By administering ethanol from E10 to E15 and examining the lumbar spinal cord on E16, we determined that ethanol can reduce motoneuron number without altering spinal cord length during more than one stage of chick embryo development, and that ethanol toxicity is not dependent on NOCD. In addition, we demonstrated that ethanol does not affect the neurotrophic content of chick muscle when it is administered from E10 to E15.

Cultured postnatal rat medial septal neurons respond to acute ethanol treatment and nerve growth factor by changing intracellular calcium levels

Ethanol neurotoxicity results in the loss of neurons during the development of the nervous system. Nerve growth factor (NGF) can ameliorate the neurotoxic effects of ethanol (EtOH) in rat medial septal (MS) neurons. These experiments study the effects of EtOH and NGF on neuronal calcium (Ca2+) homeostasis in cultured postnatal day of birth (PO) rat MS neurons. Previously, we observed that EtOH and NGF modulate intracellular Ca2+ levels [Ca2+]i) in unstimulated and high potassium stimulated (30 mM KCl) cultured rat embryonic day 21 (E21) MS neurons (Webb et al., Brain Res 701:61-74, 1995). The purpose of the present study was to explore whether the effects of EtOH and NGF on Ca2+ homeostasis were altered by developmental stage. The hypotheses tested were the following: treatment with EtOH affects Ca2+ homeostasis in postnatal day of birth (PO) rat MS neurons by causing transient and persistent changes in [Ca2+]i; NGF modulates Ca2+ homeostasis in MS neurons by regulating [Ca2+]i; the action of NGF changes the response of MS neurons to EtOH, thus altering Ca2+ homeostasis; and that EtOH and/or NGF effects on Ca2+ homeostasis are developmentally regulated. Our results indicated that behaviorally relevant levels of EtOH caused a rapid transient increase in basal [Ca2+]i, whereas there was no effect of NGF on basal [Ca2+]i. Ethanol and NGF interacted, resulting in the lowering of [Ca2+]i. During stimulation with high K+, EtOH inhibited the change in [Ca2+]i. NGF partially ameliorated this effect of higher levels of EtOH, allowing [Ca2+]i to increase. NGF and the lowest level of EtOH potentiated the high K+ stimulated increase in [Ca2+]i. Ethanol and NGF effects on [Ca2+]i were different in the PO neurons compared with our previously published observations in E21 neurons. Therefore, these data suggest that EtOH neurotoxicity and NGF protection involve mechanisms that regulate neuronal Ca2+ homeostasis, and the magnitude of these effects depend on developmental stage.

Effects of alcohol exposure and artificial rearing during development on septal and hippocampal neurotransmitters in adult rats

The effect of alcohol exposure during the early postnatal period in the rat on the hippocampus and septal region was investigated. The alcohol group was given 5 g/kg/day of ethanol from postnatal days 4 to 10 via an artificial rearing procedure. Control groups consisted of a gastrostomy control group that was treated in the same manner as the alcohol group, but not exposed to alcohol and a suckle control group that was reared normally by dams. Between 90 and 100 days of age, the hippocampus and septal region were assayed under nonstressed or stressed conditions using HPLC with electrochemical detection. Alcohol-exposed female rats exhibited increased hippocampal noradrenaline concentrations under stressed conditions, increased septal serotonin, and 5-hydroxyindoleacetic acid (5-HIAA) concentrations under nonstressed conditions, and decreased septal dopamine concentrations under stressed conditions. Artificially reared male rats (regardless of alcohol exposure) exhibited an increase in hippocampal noradrenaline concentrations under stressed conditions; a decrease in hippocampal 5-HIAA concentrations under nonstressed conditions; and a decrease in septal noradrenaline, serotonin, 5-HIAA, and dopamine concentrations under nonstressed conditions. The results suggest that female rats may be more susceptible to alcohol exposure during the postnatal period than male rats and that male rats may be more susceptible to the effects of artificial rearing than female rats.

Forebrain hypoplasia following acute prenatal ethanol exposure: quantitative analysis of effects on specific forebrain nuclei

The effects of acute prenatal exposure to ethanol on the volumes and neuronal populations of selected forebrain nuclei of postnatal animals have been examined in a mouse model. Pregnant mice were exposed to ethanol (25% ethanol, either two doses at 0.015 ml/g separated by 4 hrs, or a single dose at 0.03 ml/g) on the 8th gestational day and the cytoarchitecture of the basal forebrain, paleo- and neocortex examined quantitatively at P15. Significant reductions in the volume and total number of neurons of ventromedial and central forebrain structures, such as the olfactory bulb, septal nuclei, diagonal band nuclei and caudatoputamen, were observed in mice exposed to the divided ethanol dose, but not following the single dose. The neocortex and primary olfactory cortex were also reduced in volume in offspring exposed to the divided ethanol dose. However increased neuronal density in some neocortical regions of ethanol-exposed offspring suggests that the total number of neocortical neurons is not significantly affected by acute ethanol exposure. The findings indicate that pulse exposure to ethanol on a single day of early development causes deficits in neuronal populations of the ventromedial forebrain and caudatoputamen even in offspring without other major malformations. The results also indicate that caution should be exercised in interpreting the significance of nuclear volume reduction in human infants with fetal alcohol syndrome (FAS) in the absence of neuronal density estimates.

Protective effects of maternal buspirone treatment on serotonin reuptake sites in ethanol-exposed offspring

Previous work in this laboratory demonstrated that in utero ethanol exposure is associated with abnormal development of the serotonergic system. Specific abnormalities included deficiencies of serotonin (5-HT) and its metabolites, and cortical 5-HT reuptake sites. The concentration of 5-HT1A receptors was also altered. The serotonin deficit was detected in the fetal ethanol-exposed brain, at an age when 5-HT would normally function as an essential trophic factor. Thus, it was hypothesized that the early 5-HT ethanol-associated deficit of an essential trophic factor (e.g. 5-HT) could contribute to subsequent developmental abnormalities in serotonergic neurons. In the present investigation we used quantitative autoradiography (QAR) to more fully characterize the developmental abnormalities in 5-HT reuptake sites in developing offspring of ethanol-fed rats. In addition, we attempted to overcome the potential negative impact of the ethanol-associated deficit of fetal 5-HT, by administering a 5-HT1A agonist, buspirone, to pregnant rats. These investigations demonstrated that postnatal (PN) 19 and/or 35 day ethanol-exposed offspring had a significant decrease in [3H]citalopram binding to 5-HT reuptake sites in the frontal cortex, parietal cortex, lateral hypothalamus, substantia nigra, medial septum, and striatum. In contrast, [3H]citalopram binding was increased in the dorsal raphe on PN5 and in the median raphe on PN19. No significant ethanol-associated changes were detected in the hippocampus CA3 region or in the amygdala. When [3H]citalopram binding was compared in the offspring of saline- and buspirone-treated dams, it appeared that maternal treatment with buspirone prevented or reversed most of the ethanol-associated developmental abnormalities in 5-HT reuptake sites. Buspirone prevented the decline in binding of [3H]citalopram in the frontal cortex, lateral hypothalamus, substantia nigra and medial septum. Similarly, buspirone treatment prevented the ethanol-associated increase in binding in the dorsal and median raphe. Additional experiments are needed to elucidate the impact of maternal buspirone treatment on the development of other neurotransmitter systems in offspring.

Purkinje cell deficits in nonhuman primates following weekly exposure to ethanol during gestation

The most serious features of fetal alcohol syndrome (FAS) are mental retardation and other behavioral problems resulting from alcohol-induced damage to the developing central nervous system (CNS). The mechanism by which alcohol induces its neuroteratogenic effects is unknown. One hypothesis is that gestational alcohol exposure results in a reduction in neuronal number. This study demonstrates that gestational exposure to ethanol in a non-human primate species induces permanent dose-related deficits in the number of cerebellar Purkinje cells. Ethanol was administered via nasogastric tube once per week to 15 gravid pigtailed macaques (Macaca nemistrina) in one of the following doses: 0.0 (intubated controls), 1.2, 1.8, 2.5, 3.3, and 4.1 g/kg/dose. Offspring were reared with parental surrogates and were sacrificed at 6 months of age; 8-microns-thick, parasagittal sections were cut through the paraffin-embedded cerebellar vermis. Purkinje cells were quantified, the length of the Purkinje cell line was determined stereologically, and Purkinje cell linear frequency was calculated. The number of Purkinje cells and their linear frequencies were significantly reduced in the alcohol-treated subjects, and the deficits were dose-dependent. The groups receiving 2.5 g/kg/dose and above were most severely affected and had an average deficit in Purkinje cell number of 11.8%, relative to controls. Alcohol had no effect on the length of the Purkinje cell line. The findings suggest that alcohol-induced reduction in neuronal number may be an important factor underlying the CNS dysfunction in FAS.

Ethanol alters spatial processing of hippocampal place cells: a mechanism for impaired navigation when intoxicated

This study describes a new mechanism by which ethanol alters brain function and may impair performance on tasks requiring spatial navigation. Recording electrophysiological activity from single neurons in the awake, freely behaving animal, the present study shows that ethanol impairs the ability of place cells in the hippocampus to process spatial information. The impairment by ethanol in spatial processing of place cells was remarkably similar to the impairment produced by lesions of afferents to the hippocampus, except that the effect of ethanol was reversible. Since lesions to hippocampal afferents that alter spatial processing of place cells concomitantly impair spatial navigation, the present results suggest that ethanol similarly impairs spatial navigation by altering spatial processing of place cells. The present results have implications for the observation that ethanol impairs performance on navigational tasks that require spatial processing, such as automobile driving.