Developmental changes in the brain levels of neurotransmitters as influenced by maternal ethanol consumption in the rat

Synaptic Plasticity Abnormalities in Fetal Alcohol Spectrum Disorders

The brain's ability to strengthen or weaken synaptic connections is often termed synaptic plasticity. It has been shown to function in brain remodeling following different types of brain damage (e.g., drugs of abuse, alcohol use disorders, neurodegenerative diseases, and inflammatory conditions). Although synaptic plasticity mechanisms have been extensively studied, how neural plasticity can influence neurobehavioral abnormalities in alcohol use disorders (AUDs) is far from being completely understood. Alcohol use during pregnancy and its harmful effects on the developing offspring are major public health, social, and economic challenges. The significant attribute of prenatal alcohol exposure on offspring is damage to the central nervous system (CNS), causing a range of synaptic structural, functional, and behavioral impairments, collectively called fetal alcohol spectrum disorder (FASD). Although the synaptic mechanisms in FASD are limited, emerging evidence suggests that FASD pathogenesis involves altering a set of molecules involved in neurotransmission, myelination, and neuroinflammation. These studies identify several immediate and long-lasting changes using many molecular approaches that are essential for synaptic plasticity and cognitive function. Therefore, they can offer potential synaptic targets for the many neurobehavioral abnormalities observed in FASD. In this review, we discuss the substantial research progress in different aspects of synaptic and molecular changes that can shed light on the mechanism of synaptic dysfunction in FASD. Increasing our understanding of the synaptic changes in FASD will significantly advance our knowledge and could provide a basis for finding novel therapeutic targets and innovative treatment strategies.

Neonatal ethanol causes profound reduction of cholinergic cell number in the basal forebrain of adult animals

In animal models that mimic human third-trimester fetal development, ethanol causes substantial cellular apoptosis in the brain, but for most brain structures, the extent of permanent neuron loss that persists into adulthood is unknown. We injected ethanol into C57BL/6J mouse pups at postnatal day 7 (P7) to model human late-gestation ethanol toxicity, and then used stereological methods to investigate adult cell numbers in several subcortical neurotransmitter systems that project extensively in the forebrain to regulate arousal states. Ethanol treatment caused especially large reductions (34-42%) in the cholinergic cells of the basal forebrain, including cholinergic cells in the medial septal/vertical diagonal band nuclei (Ch1/Ch2) and in the horizontal diagonal band/substantia innominata/nucleus basalis nuclei (Ch3/Ch4). Cell loss was also present in non-cholinergic basal forebrain cells, as demonstrated by 34% reduction of parvalbumin-immunolabeled GABA cells and 25% reduction of total Nissl-stained neurons in the Ch1/Ch2 region. In contrast, cholinergic cells in the striatum were reduced only 12% by ethanol, and those of the brainstem pedunculopontine/lateral dorsal tegmental nuclei (Ch5/Ch6) were not significantly reduced. Similarly, ethanol did not significantly reduce dopamine cells of the ventral tegmental area/substantia nigra or serotonin cells in the dorsal raphe nucleus. Orexin (hypocretin) cells in the hypothalamus showed a modest reduction (14%). Our findings indicate that the basal forebrain is especially vulnerable to alcohol exposure in the late gestational period. Reduction of cholinergic and GABAergic projection neurons from the basal forebrain that regulate forebrain arousal may contribute to the behavioral and cognitive deficits associated with neonatal ethanol exposure.

Effects of gestational thiamine-deprivation and/or exposure to ethanol on crucial offspring rat brain enzyme activities

OBJECTIVE

The fetal alcohol spectrum disorder (FASD) is a group of clinical conditions associated with the in utero exposure to ethanol (EtOH). We have recently examined the effects of a moderate maternal exposure to EtOH on crucial brain enzyme activities in offspring rats, and discussed the translational challenges arising when attempting to simulate any of the clinical conditions associated with FASD.

MATERIALS AND METHODS

In this current study, we: (i) address the need for a more consistent and reliable in vivo experimental platform that could simulate milder cases of FASD complicated by simultaneous thiamine-deprivation during gestation and (ii) explore the effects of such a moderate maternal exposure pattern to EtOH and a thiamine-deficient diet (TDD) on crucial enzyme activities in the offspring rat brains.

RESULTS

We demonstrate a significant decrease in the newborn and 21-day-old offspring body and brain weight due to maternal dietary thiamine-deprivation, as well as evidence of crucial brain enzyme activity alterations that in some cases are present in the offspring rat brains long after birth (and the end of the maternal exposure to both EtOH and TDD).

CONCLUSIONS

Our findings provide a preliminary characterization of important neurochemical effects due to maternal exposure to EtOH and TDD during gestation that might affect the offspring rat neurodevelopment, and that characterization should be further explored in a brain region-specific manner level as well as through the parallel examination of changes in the offspring rat brain lipid composition.

Exposure to ethanol during neurodevelopment modifies crucial offspring rat brain enzyme activities in a region-specific manner

The experimental simulation of conditions falling within "the fetal alcohol spectrum disorder" (FASD) requires the maternal exposure to ethanol (EtOH) during crucial neurodevelopmental periods; EtOH has been linked to a number of neurotoxic effects on the fetus, which are dependent upon the extent and the magnitude of the maternal exposure to EtOH and for which very little is known with regard to the exact mechanism(s) involved. The current study has examined the effects of moderate maternal exposure to EtOH (10 % v/v in the drinking water) throughout gestation, or gestation and lactation, on crucial 21-day-old offspring Wistar rat brain parameters, such as the activities of acetylcholinesterase (AChE) and two adenosine triphosphatases (Na(+),K(+)-ATPase and Mg(2+)-ATPase), in major offspring CNS regions (frontal cortex, hippocampus, hypothalamus, cerebellum and pons). The implemented experimental setting has provided a comparative view of the neurotoxic effects of maternal exposure to EtOH between gestation alone and a wider exposure timeframe that better covers the human third trimester-matching CNS neurodevelopment period (gestation and lactation), and has revealed a CNS region-specific susceptibility of the examined crucial neurochemical parameters to the EtOH exposure schemes attempted. Amongst these parameters, of particular importance is the recorded extensive stimulation of Na(+),K(+)-ATPase in the frontal cortex of the EtOH-exposed offspring that seems to be a result of the deleterious effect of EtOH during gestation. Although this stimulation could be inversely related to the observed inhibition of AChE in the same CNS region, its dependency upon the EtOH-induced modulation of other systems of neurotransmission cannot be excluded and must be further clarified in future experimental attempts aiming to simulate and to shed more light on the milder forms of the FASD-related pathophysiology.

The effects of postnatal alcohol exposure and galantamine on the context pre-exposure facilitation effect and acetylcholine efflux using in vivo microdialysis

Fetal alcohol spectrum disorders (FASD) are characterized by damage to multiple brain regions, including the hippocampus, which is involved in learning and memory. The acetylcholine neurotransmitter system provides major input to the hippocampus and is a possible target of developmental alcohol exposure. Alcohol (3.0 g/kg/day) was administered via intubation to male rat pups (postnatal day [PD] 2-10; ethanol-treated [ET]). Controls received a sham intubation (IC) or no treatment (NC). Acetylcholine efflux was measured using in vivo microdialysis (PD 32-35). ET animals were not different at baseline, but had decreased K(+)/Ca(2+)-induced acetylcholine efflux compared to NC animals and an enhanced acetylcholine response to galantamine (acetylcholinesterase inhibitor; 2.0 mg/kg) compared to both control groups. A separate cohort of animals was tested in the context pre-exposure facilitation effect task (CPFE; PD 30-32) following postnatal alcohol exposure and administration of galantamine (2.0 mg/kg; PD 11-30). Neither chronic galantamine nor postnatal alcohol exposure influenced performance in the CPFE task. Using immunohistochemistry, we found that neither alcohol exposure nor behavioral testing significantly altered the density of vesicular acetylcholine transporter or alpha7 nicotinic acetylcholine receptor in the ventral hippocampus (CA1). In the medial septum, the average number of choline acetyltransferase (ChAT+) cells was increased in ET animals that displayed the context-shock association; there were no changes in IC and NC animals that learned the context-shock association or in any animals that were in the control task that entailed no learning. Taken together, these results indicate that the hippocampal acetylcholine system is significantly disrupted under conditions of pharmacological manipulations (e.g., galantamine) in alcohol-exposed animals. Furthermore, ChAT was up‑regulated in ET animals that learned the CPFE, which may account for their ability to perform this task. In sum, developmental alcohol exposure may disrupt learning and memory in adolescence via a cholinergic mechanism.

Brain malformations in prenatal mice following acute maternal ethanol administration

Acute maternal ethanol administration (two i.p. injections of 2.9 g ethanol/kg maternal body wt) to C57B1/6J mice during gastrulation stages of embryogenesis (gestational day 7) induces a spectrum of brain and facial malformations characteristic of those seen in the human Fetal Alcohol Syndrome. Scanning electron microscopic and light microscopic analyses of the brains of embryos of gestational days 11-14 demonstrate ventro-medial forebrain deficiencies of varying degrees of severity in affected specimens. Even at the mild end of the spectrum, reductions in the size of the septal nuclei and the shape of the third ventricle are observed. As the severity of the effect increases, the septal nuclei disappear altogether, resulting in midline fusion of the corpora striata (basal ganglia). In such cases, the third ventricle is totally absent anteriorly (preoptic area) and significantly narrowed at more posterior levels, adjacent to the ventromedial nuclei. In addition, the hippocampal primordium is absent at levels which include the corpora striata, and septation of the cerebral cortex is incomplete. More posteriorly, at the level of the posterior commissure, the hippocampal primordium is present, but greatly reduced in size, and the entire brain is distinctly narrower in width. Still further posteriorly, at levels of the metencephalon which include the tectum and cerebellar plate, the cerebral aqueduct is significantly expanded, fusion of midline (raphe) structures is incomplete and the cerebellar plate does not extend as far medially as it does normally. Interestingly, these abnormalities are analogous to those observed in the holoprosencephaly series of malformations. The results of the present study support our hypothesis that severe forms of the Fetal Alcohol Syndrome mimic certain aspects of the holoprosencephaly spectrum, and indicate that special attention should be paid to possible deficiencies in the septal nuclei and basal ganglia of children born to women who abuse alcohol. The fact that gross brain malformations can be induced in this animal model at a time corresponding to the third week of human gestation (a time when most women remain unaware of pregnancy) is of significance in terms of the possible prevention of alcohol-induced birth defects and mental deficiency in man.

The effects of perinatal choline supplementation on hippocampal cholinergic development in rats exposed to alcohol during the brain growth spurt

Prenatal alcohol exposure leads to long-lasting cognitive and attention deficits, as well as hyperactivity. Using a rat model, we have previously shown that perinatal supplementation with the essential nutrient, choline, can reduce the severity of some fetal alcohol effects, including hyperactivity and deficits in learning and memory. In fact, choline can mitigate alcohol-related learning deficits even when administered after developmental alcohol exposure, during the postnatal period. However, it is not yet known how choline is able to mitigate alcohol-related behavioral alterations. Choline may act by altering cholinergic signaling in the hippocampus. This study examined the effects of developmental alcohol exposure and perinatal choline supplementation on hippocampal M(1) and M(2/4) muscarinic receptors. Sprague-Dawley rat pups were orally intubated with ethanol (5.25 mg/kg/day) from postnatal days (PD) 4-9, a period of brain development equivalent to the human third trimester; control subjects received sham intubations. From PD 4-30, subjects were injected s.c. with choline chloride (100 mg/kg/day) or saline vehicle. Open field activity was assessed from PD 30 through 33, and brain tissue was collected on PD 35 for autoradiographic analysis. Ethanol-exposed subjects were more active compared to controls during the first 2 days of testing, an effect attenuated with choline supplementation. Developmental alcohol exposure significantly decreased the density of muscarinic M(1) receptors in the dorsal hippocampus, an effect that was not altered by choline supplementation. In contrast, developmental alcohol exposure significantly increased M(2/4) receptor density, an effect mitigated by choline supplementation. In fact, M(2/4) receptor density of subjects exposed to alcohol and treated with choline did not differ significantly from that of controls. These data suggest that developmental alcohol exposure can cause long-lasting changes in the hippocampal cholinergic system and that perinatal choline supplementation may attenuate alcohol-related behavioral changes by influencing cholinergic systems.

Neonatal alcohol-induced region-dependent changes in rat brain neurochemistry measured by high-resolution magnetic resonance spectroscopy

BACKGROUND

Maternal drinking during pregnancy can lead to a range of deleterious outcomes in the developing offspring that have been collectively termed fetal alcohol spectrum disorders (FASDs). There is interest and recognized value in using non-invasive neuroimaging techniques such as magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) to characterize, respectively, structural and biochemical alterations in individuals with FASDs. To date, however, results with MRS have been inconsistent regarding the degree and/or nature of abnormalities.

METHODS

High-resolution magic angle spinning (HR-MAS) proton ((1)H) MRS is an ex vivo neuroimaging technique that can acquire spectra in small punches of intact tissue, providing clinically relevant neurochemical information about discrete brain regions. In this study, HR-MAS (1)H MRS was used to examine regional neurochemistry in frontal cortex, striatum, hippocampus, and cerebellum of young rats previously exposed to ethanol as neonates. Key neurochemicals of interest included N-acetyl-aspartate (NAA), glutamate, GABA, glutamine, creatine, choline and myo-inositol.

RESULTS

Daily neonatal alcohol exposure from postnatal day 4 (PN4) through PN9 significantly reduced levels of NAA and taurine in the cerebellum and striatum, and induced sex-dependent reductions in cerebellar glutamate when measured on PN16. In addition, myo-inositol was significantly increased in cerebellum. The frontal cortex and hippocampus were virtually unaffected by this neonatal alcohol exposure.

CONCLUSION

Results of this research may have implications for understanding the underlying neurobiology associated with FASDs and aid in testing treatments in the future. Ongoing studies are assessing the developmental persistence of and/or maturational recovery from these changes.

Impaired trace fear conditioning following neonatal ethanol: reversal by choline

Neonatal ethanol exposure in animals results in performance deficits on tests of hippocampus-dependent spatial memory, and recent studies have shown that extra dietary choline can ameliorate some of these impairments. In this experiment, rats were administered 5.25 g/kg ig ethanol per day or sham intubations on Postnatal Days (PD) 4-9 and choline (0.1 ml of an 18.8 mg/ml solution) or saline subcutaneously on PD 4-20. On PD 30, rats were given delay or trace fear conditioning trials and were tested for conditioned stimulus-elicited freezing 24 hr later. Neonatal ethanol produced a profound impairment in trace conditioning that was reversed by choline. Groups did not differ in delay conditioned responding, indicating that neonatal ethanol produces a relatively selective cognitive deficit that can be alleviated with supplemental choline.

Ethanol modulates the expression of GABAB receptor mRNAs in the prenatal rat brain in an age and area dependent manner

Prenatal ethanol exposure has various deleterious effects on neuronal development. As GABA(B) receptor is known to play an important role during the development of the CNS, we now focused on its mRNA expression pattern in the rat brain during the late gestational days (GD) from 15.5 to GD 21.5. Ethanol's effect was also observed from GD 11.5 to GD 21.5. GABA(B1) receptor mRNA showed a high expression level in GD 15.5 and 19.5, while GABA(B2) receptor mRNA did in GD 15.5 and 21.5. The mRNAs levels depended on age and area during development. Ethanol exposure decreased GABA(B1) receptor from GD 11.5 to GD 19.5 with slight increases in GD 21.5. The decreasing effects were area dependent, with the highest effects in the forebrain including cortex, whereas slight effects were observed in the midbrain and hindbrain. The present results suggest an important role of GABA(B) receptor in the effects of ethanol on prenatal brain developmental processes.

Effects of ethanol on development of locus coeruleus brain stem transplants in oculo

In this investigation, we studied the effects of ethanol (EtOH) on the development of noradrenergic (NE) neurons of the locus coeruleus. Fetal brainstem tissue from embryonic days 15-17 was grafted into the anterior chamber of the eye of adult rats. Two different experimental groups were exposed to 16% EtOH in the drinking water during different developmental windows. The first group received EtOH 24 h after transplantation and during the whole experimental period of 7 weeks (continuous EtOH), and the second group only during the last 5 weeks of the experimental period (delayed EtOH). The control group received water ad libitum. After 7 weeks, all the animals were sacrificed and morphological evaluations were performed. Immunohistochemical analysis showed that axon bundle formation and NE fiber outgrowth into the host iris was significantly reduced in the continuous EtOH-treated group compared to controls. We also studied the morphology of TH-positive neurons and processes in the intraocular transplants. A significant decrease in TH-positive staining intensity was observed in the continuous EtOH-treated group compared to controls. Moreover, we found a significant decrease in cell size and neuronal survival in both EtOH-treated groups compared to controls. The present results suggest that chronic EtOH exposure during development leads to an altered axonal outgrowth and decreased cell sizes and number of NE neurons in intraocular brain stem grafts. Furthermore, we found that NE neurons are more sensitive to EtOH exposure during the last prenatal days and the first postnatal week of development, compared to a later developmental period.

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.

Effects of prenatal ethanol exposure on hippocampal theta activity in the rat

This study examined the effects of prenatal ethanol exposure on hippocampal theta activity in adult rats. Subjects were randomly selected from four prenatal treatment conditions: untreated, 0, 3, or 5 g/kg/day ethanol. At approximately 90 days of age, all subjects were surgically implanted with a bipolar electrode in the CA1 region of the hippocampus. Four epochs of hippocampal theta rhythm activity were recorded while the subjects were moving and four more while still, and a normalized theta score was computed and compared among groups. The 5 g/kg male group demonstrated a significantly higher theta score than controls, indicating either an increase in type I (movement-associated) theta and/or a decrease in type II (information-processing) theta activity. These results are consistent with prior reports that prenatal ethanol exposure alters hippocampal function and support clinical indications that monitoring the EEG of children may prove to be useful in the diagnosis of fetal alcohol syndrome and/or the detection of alcohol-related birth defects.

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.

Spatial learning in rats exposed to acute ethanol intoxication on gestational day 8

Pregnant Wistar rats were treated on gestational day 8 (GD 8) with two IP injections of either ethanol (2.9 g/kg in 24% v/v saline solution) or saline. Offspring were tested in the water-maze task at 45 or 90 days of age. The escape latencies of rats trained with a submerged escape platform at a fixed location were similar between control and experimental rats. Analyses of responses on a probe trial carried out 10 days after the training period, revealed that 90-day-old females prenatally exposed to alcohol were less likely to swim in the target region. No differences were observed in this free-swim trial in 45- and 90-day-old male, and 45-day-old female animals. Binding studies of low-affinity GABAA sites in the hippocampus showed an increase in affinity of [3H]GABAA for their binding sites in 90-day-old female offspring prenatally intoxicated with ethanol. Our results demonstrate that acute intoxication with ethanol on GD 8 did not modify acquisition but impaired the retention of spatial learning only in adult female rats. It is possible that the impaired retention will be consequence of higher GABAA receptor affinity.

Influence of prenatal ethanol exposure on cholinergic development in the rat striatum

This study investigated the influence of ethanol exposure throughout gestation on cholinergic development within the rat striatal region. Pregnant Long-Evans rats were maintained on three diets throughout gestation: A liquid diet in which ethanol accounted for 35-39% of the total calories, a similar diet with the isocaloric substitution of sucrose for ethanol, and a lab chow control diet. At postnatal days 14 and 60 (P14 and P60), the striatal regions of the offspring were analyzed for the number of cholinergic neurons, via choline acetyltransferase (ChAT) immunostaining. The area of the striatum was also measured in these animals. At P14, P21, and P60, ChAT activity was assessed in the same region. These analyses revealed a significant increase in the number of cholinergic striatal neurons at P14 in the animals which had been exposed prenatally to ethanol. This increase was transient, however, with equal numbers of ChAT-positive cells found in all three groups by adulthood (P60). The brain weights of the ethanol-exposed animals were significantly reduced at P14 and P21, but were comparable to controls by P60. There were no significant differences in the striatal area or the overall volume of the region assessed, however, at either P14 or P60. Although there were some increases in ChAT activity across the ages viewed (most notably between P14 and P21), there were no effects of diet on ChAT activity at any age assessed. It is proposed that the increased numbers of cholinergic neurons could be a function of errors in migration, enhanced neurogenesis, diminished cell death, alterations in gene expression, or increased cell survival as a result of alterations in neurotrophic factor production or availability.

Perturbation of target-directed neurite outgrowth in embryonic CNS co-cultures grown in the presence of ethanol

Studies were conducted to determine the influence of ethanol on target-directed fiber outgrowth in culture, using embryonic chick spinal cord-muscle, and fetal rat septal-hippocampal co-cultured explants. Process extension from the spinal cord and septal explants in control cultures was selectively oriented toward the appropriate target tissue. Ethanol in the culture medium (500 mg/dl) eliminated this target-oriented outgrowth in both systems, although the overall extent of neurite outgrowth was not affected. In an effort to further characterize the source of this disruption, target explants were grown alone, with and without ethanol, and the target-conditioned culture media was subsequently harvested and placed on newly plated spinal cord or septal explants, to determine whether ethanol decreased the target production of soluble substances. To determine whether deposition of substrate-bound materials by the target tissue was affected by ethanol, spinal cord or septal explants were plated in wells which had previously been occupied by the appropriate target tissue. These studies revealed that ethanol significantly inhibited production of soluble and substrate-bound materials by muscle explants, but not by hippocampal explants. It was concluded that the ethanol-induced loss of target-directed neurite outgrowth in the spinal cord explants could be accounted for primarily by the attenuated production of neurotropic/neurotropic substances by the muscle tissue. The loss of target-directionality in the septal explants appeared to be due to other factors, possibly related to ethanol-induced compromise of the capacity of the septal neurons to respond appropriately to target-derived neurotrophic/neurotropic substances. The implications of these results for the fetal alcohol syndrome are considered.

Alterations of the thalamo-cortical system in rats prenatally exposed to ethanol are prevented by concurrent administration of acetyl-L-carnitine

We previously demonstrated that adult rats prenatally exposed to ethanol display permanent damages of thalamo-cortical connections [18,19,33]. Here the effect of simultaneous administration of ethanol and acetyl-L-carnitine has been investigated. Adult animals underwent cortical or thalamic injections of horseradish peroxidase and both anterograde and retrograde thalamic and cortical labeling have been analyzed. Ethanol-induced changes of thalamo-cortical circuits are prevented by concurrent administration of acetyl-L-carnitine. Possible mechanisms underlying this effect are discussed.

Chronic prenatal ethanol exposure alters the normal ontogeny of choline acetyltransferase activity in the rat septohippocampal system

In animal models of fetal alcohol syndrome (FAS), the hippocampus has been shown to be especially sensitive to the effects of prenatal ethanol exposure, exhibiting neuronal loss and alterations in neuritic process elaboration. We have characterized the influence of chronic prenatal ethanol treatment (CPET) on the postnatal expression of choline acetyltransferase (ChAT) in the hippocampus and the septal area that contains neurons that provide the primary cholinergic innervation to the hippocampus. On gestation days 1-22, pregnant rats were either fed an ethanol-containing liquid diet, pair-fed a calorically equivalent sucrose-containing diet, or given rat chow ad libitum. In Chow control animals, the ontogenetic progression of ChAT activity in the septal area and hippocampus was characterized by a significant period of upregulation during the 2nd and 3rd postnatal weeks, exhibiting and an approximate 5-fold increase (septal area) and 7-fold increase (hippocampus) by postnatal day 21 (P21). At P14, ethanol exposure reduced septal and hippocampal ChAT activity levels, compared with those of pair-fed offspring. ChAT activity reached control levels by P21 in ethanol-exposed pups, suggesting that the earlier decline in activity may reflect a delay in the ontogenetic upregulation. In addition, there was a trend toward increased septal and hippocampal ChAT activities at P1 and P7 in both liquid diet groups. This liquid diet-stimulated increase may mask the effects of ethanol on early postnatal ChAT expression in the septohippocampal system. The results suggest that prenatal ethanol exposure may influence factors that regulate the developmental expression of ChAT in the septohippocampal system.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of prenatal ethanol exposure on the hippocampal neurochemistry of albino rats at 90 days of postnatal age

OBJECTIVE

Our purpose was to test the hypothesis that prenatal ethanol exposure alters the hippocampal muscarinic cholinergic neurochemistry of albino rats.

STUDY DESIGN

Ethanol was administered in a liquid diet to pregnant albino Sprague-Dawley rats. Liquid diet control animals received the same diet in which ethanol was replaced by an isocaloric amount of maltose-dextrin. Chow-fed control animals were fed laboratory chow as desired. Progeny were killed at 90 days of age, and their hippocampi were analyzed for muscarinic cholinergic receptors by use of tritiated quinuclidinyl benzilate.

RESULTS

Prenatal ethanol exposure produced a statistically significant decrease in the number of muscarinic receptors in males. Similar trends were noted in females, but the results were not statistically significant.

CONCLUSION

Prenatal ethanol treatment caused long-lasting alterations in the muscarinic cholinergic receptors of the hippocampus in male rats.

Effect of prenatal ethanol and stress on levels of beta-endorphin in different brain regions of the rat

The combination of prenatal ethanol exposure and footshock stress was investigated for its effects on brain beta-endorphin levels. Subjects were offspring of rats that received 1 of 3 prenatal dietary treatments: an ethanol-containing liquid diet, a identical liquid diet with ethanol substituted isocalorically with maltose-dextrin (pair-fed group), and standard laboratory rat chow (chow-fed group). Two different stress paradigms were used: a short (30-sec) footshock stress paradigm and a prolonged (180-sec) footshock stress paradigm. Levels of beta-endorphin were measured with radioimmunoassay in eight brain regions of unstressed (baseline) rats, and of stressed rats at 3 and 30 min following termination of the stress. Seven brain regions containing high densities of beta-endorphin axons and terminals were chosen, as well as the arcuate region of the hypothalamus, the only brain region where both beta-endorphin perikarya and terminals are located. Following the short footshock stress paradigm, there were no changes in beta-endorphin levels, except for a trend toward increased levels in the pair-fed group. After the prolonged stress paradigm, levels of beta-endorphin in both the pair-fed and chow-fed groups tended to be decreased in several brain regions, including the arcuate region, at 3 min after termination of the stress. In contrast, for the prenatally ethanol-exposed group, beta-endorphin levels were increased significantly in the arcuate region, and moderately increased in the septal/preoptic region and medulla/pons at 3 min after the prolonged stress paradigm.(ABSTRACT TRUNCATED AT 250 WORDS)

Ethanol elevates fetal serum glutamate levels in the rat

Glutamate is an important excitatory neurotransmitter. However, a sustained elevation of glutamate in the extracellular space may be toxic to neurons. Because the blood-brain barrier is incomplete in the developing fetus, an elevation of fetal serum glutamate could expose the immature, growing brain to potentially toxic levels of extracellular glutamate. Chronic ethanol consumption during pregnancy is associated with an increased risk for a complex array of congenital anomalies, including alterations in the CNS, a hallmark of the fetal alcohol syndrome. Some central nervous system changes appear to involve the glutamate receptor, including reduced number and altered function. One mechanism for receptor downregulation may be a sustained elevation in extracellular glutamate. We hypothesize that chronic ethanol exposure during pregnancy leads to an elevation in fetal serum glutamate. When rats were fed ethanol-containing liquid diet throughout pregnancy, growth retardation of fetuses was observed at sacrifice (gestation day 20). Within each group, ethanol-fed, pair-fed, and ad libitum chow-fed, serum glutamate levels were generally higher in the fetus than in the dam. Ethanol treatment had no effect on fetal or maternal serum glutamine, a reciprocal metabolite of glutamate. In contrast, ethanol treatment increased serum glutamate levels in the fetal serum by nearly 50%, compared with either of the control groups. Maternal serum glutamate was not affected. The finding of ethanol-induced elevation of fetal serum glutamate suggests that the developing brain might be concurrently exposed to elevated levels of extracellular glutamate. Chronic exposure to elevated glutamate during critical periods of brain development may contribute to the pathogenesis of the fetal alcohol syndrome.

Ethanol influences on the chick embryo spinal cord motor system: analyses of motoneuron cell death, motility, and target trophic factor activity and in vitro analyses of neurotoxicity and trophic factor neuroprotection

A series of in vivo and in vitro experiments were conducted to determine the influence of prenatally administered ethanol on several aspects of the developing chick embryo spinal cord motor system. Specifically, we examined: (1) the effect of chronic ethanol administration during the natural cell death period on spinal cord motoneuron numbers; (2) the influence of ethanol on ongoing embryonic motility; (3) the effect of ethanol exposure on neurotrophic activity in motoneuron target tissue (limb bud); and (4) the responsiveness of cultured spinal cord neurons to ethanol, and the potential of target-derived neurotrophic factors to ameliorate ethanol neurotoxicity. These studies revealed the following: Chronic prenatal ethanol exposure reduces the number of motoneurons present in the lateral motor column after the cell death period [embryonic day 12 (E12)]. Ethanol tends to inhibit embryonic motility, particularly during the later stages viewed (E9-E11). Chronic ethanol exposure reduces the neurotrophic activity contained in target muscle tissue. Such diminished support could contribute to the observed motoneuron loss. Direct exposure of spinal cord neurons to ethanol decreases neuronal survival and process outgrowth in a dose-dependent manner, but the addition of target muscle extract to ethanol-containing cultures can ameliorate this ethanol neurotoxicity. These studies demonstrate ethanol toxicity in a population not previously viewed in this regard and suggest a mechanism that may be related to this cell loss (i.e., decreased neurotrophic support).

Chronic ethanol alters CNS cholinergic and cerebellar development in chick embryos

Chick embryos were given daily injections of ethanol (approximately 30 mg/day) either chronically from embryonic days 4 to 15 (E4-E15) or E18, or acutely from E15 to E18. Untreated and saline-injected embryos served as controls. Although morphological indicators of developmental age were not different among groups, chronic ethanol reduced weights of several brain regions. Similar to rodent models of prenatal ethanol exposure, chronic ethanol treatment reduced cerebellar Purkinje cell numbers compared to controls. Chronic but not acute ethanol exposure resulted in a significant reduction in choline acetyltransferase activity in the optic tectum (OT) and forebrain (FB) compared with controls. This study demonstrates that the chick embryo is a viable model to investigate the effects of ethanol exposure on CNS development. Unlike the mammalian fetus, the avian embryo is isolated from maternal interactions and may prove more useful in investigating the mechanisms by which ethanol directly influences brain development.

Prenatal ethanol exposure affects the activity and mRNA expression of neuronal membrane enzymes in rat offspring

In order to elucidate molecular mechanisms underlying brain dysfunction in offspring exposed to ethanol in utero, subclinical doses of ethanol that do not have apparent structural effect on the offspring were administered intraperitoneally to pregnant rats at various gestational stages. We measured the activity of membrane marker enzymes and the level of mRNA of myelin proteins of the offspring brain. The activity of a myelin specific enzyme, 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNP) decreased in ethanol-exposed offspring. This effect was not related to the period of gestation or the dose of ethanol. Perikaryonal enzymes, acetylcholinesterase and Na+, K(+)-ATPase, were significantly affected in groups exposed to ethanol at early fetal stage and in high doses. Expression of mRNAs of CNP and myelin basic proteins decreased significantly in the ethanol-treated group, with abnormal developmental profile suggesting a relationship with delayed myelination in offspring exposed to ethanol in utero. The present findings suggest that in spite of the low doses of ethanol that do not cause clinical symptoms in the offspring, prenatal exposure to ethanol affects the level of mRNA of membrane enzyme proteins in the offspring brain, consequently causing a corresponding reduction in enzyme activity, that may lead to neuronal dysfunction. In a separate study, blood ethanol levels were found to reach a maximum level within 30 min after injection and be undetectable after 5 to 10 h. No accumulation effects due to daily injection were observed.

Prenatal ethanol exposure: changes in regional brain catecholamine content following stress

Previous studies have shown that fetal ethanol exposure (FEE) may have long-term effects on the function of catecholaminergic neurons in different regions of the CNS. The present study is the first to examine the effects of FEE on regional brain catecholamine responses following acute stress (a single 60-min restraint stress), repeated stress (single periods of restraint stress on 1, 5, or 10 consecutive days), and recovery from stress (recovery for up to 60 min in the home cage following a single 60-min period of restraint stress). Both male and female offspring from FEE, pair-fed (PF), and ad libitum-fed control (C) groups were tested in adulthood to determine catecholamine content in the cortex, hypothalamus, and hippocampus. A single period of restraint reduced cortical norepinephrine (NE) content in FEE and PF animals compared with that in the cortex of C animals, and reduced hypothalamic NE content in FEE female offspring below that found in animals in all other groups. In contrast, hippocampal NE content was higher in FEE than in C animals following a single period of restraint; PF animals had intermediate levels of hippocampal NE and did not differ significantly from either FEE or C animals. Following repeated periods of restraint, cortical NE content was lower in FEE than in C animals; PF animals once again had intermediate levels of NE. Importantly, basal (nonstressed) NE content did not differ among groups in any brain area examined. In addition, several significant changes in regional brain catecholaminergic responses to acute stress were observed in animals across all treatment groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Scopolamine does not differentially affect Morris maze performance in adult rats exposed prenatally to alcohol

Rats exposed prenatally to alcohol have shown deficits in spatial learning in radial-arm and Morris mazes. Prenatal exposure to alcohol in rats has also been shown to alter central nervous system (CNS) cholinergic function. Since cholinergic dysfunction disrupts spatial learning in normal rats, the present experiment assessed the role of putative prenatal alcohol-induced cholinergic dysfunction in spatial learning in rats. Pregnant rats were fed alcohol via liquid diet from gestation day 6 to 20. Control dams were pair-fed liquid diet without alcohol or fed ad lib lab chow and water. Group housed adult male and female offspring (postnatal days 110 to 135) were given scopolamine-HCl (0, 0.5, or 1.0 mg/kg/day) and tested in a Morris maze, with four trials per day for four days. A 15-s probe trial preceded testing on days 2-4. On day 5, the rats were given four trials to learn a new platform location. Scopolamine produced dose-dependent increases in latency to find the platform for all groups. There were no significant differences among prenatal treatment groups in scopolamine-induced shifts in performance. The results did not support the hypothesis that prenatal alcohol-induced CNS cholinergic dysfunction is related to spatial learning performance in these rats.

Cholinergic mechanisms in physical dependence on barbiturates, ethanol and benzodiazepines

The aim of this review is to summarize the effects of acute and chronic treatment with barbiturates, ethanol and benzodiazepines on cholinergic mechanisms in the brains of experimental animals. A single dose of each of these substances reduces the turnover of ACh in the brain. Long-term treatment has the opposite effect; complicated interactions including decreased content of ACh are induced. Barbiturates have been shown to bind stereospecifically to muscarinic and nicotinic receptors in the brain, but this has not been observed for ethanol or the benzodiazepines. The effects on the cholinergic system are affected by the length of treatment and choice of treatment regimen. No effect on cholinergic parameters, such as muscarinic receptors, in the brain is observed on withdrawal of ethanol or barbiturate treatment when the animals are still tolerant towards the substances. The increase in the number of muscarinic receptors observed in several brain regions on withdrawal is seen as a sign of cholinergic supersensitivity. The number of receptors returns to normal when abstinence convulsions have occurred. The assumption of a cholinergic influence is supported by the finding that atropine, given as a single dose on the day of withdrawal of barbital, can prevent the muscarinic receptor changes. Furthermore, long-term barbital or ethanol treatment can induce permanent persistent changes in the cholinergic system in the brain. Cognitive defects and a significant permanent reduction in the content of ACh can be measured in rats which have had long-term barbital treatment. Similarly, a reduced number of muscarinic receptors has been measured in different brain regions of chronic alcoholics. Accumulating data support the role of the cholinergic system in expressing symptoms of physical dependence on barbiturates, ethanol and benzodiazepines as well as in the permanent long-term effects observed after end of treatment.

Acute ethanol intoxication during pregnancy: postnatal effects on the behavioral response to serotonin agents

Pregnant wistar rats were treated on the eighth day of gestation (GD 8) with two IP injections, spaced by 4 h, of either ethanol (2.9 g/kg in 24% v/v saline solution, EG) or saline (SG). Other pregnant females did not received any type of IP injections (absolute control group, ACG). Offspring were tested at 45 or 90 days of age. At 45 days of age, EG showed an increased behavioral response (forepaw treading and hindlimb abduction) to the 5-HT1 agonist, 5-methoxy-N,N-dymethyltryptamine. In addition, an enhanced "wet-dog" shakes behavioral response to 5-HT2 agonist, 5-hydroxy-L-tryptophan, was also observed in EG as compared to ACG and SG. On the contrary, at 90 days, EG exhibited a diminished behavioral reactivity to 5-HT1 and 5-HT2 agonists as compared to SG. These results demonstrated that acute administration of ethanol on GD 8 induced long-lasting changes in the functioning of central serotonergic systems.

Effects of ethanol on development of dorsal raphe transplants in oculo: a morphological and electrophysiological study

The purpose of this project was to investigate ethanol influence on the development of serotonin-containing (5-HT) neurons of the dorsal raphe nucleus in rat. Fetal tissue of embryonic day 17 from the dorsal brainstem was grafted to the anterior chamber of the eye of adult albino rats. The experimental group was exposed to 16% ethanol in the drinking water, and the control group received water ad libitum. After 4 weeks, morphological and electrophysiological evaluations were performed. Immunohistochemical analysis showed that 5-HT-immunoreactive fibers from ethanol-treated transplants had a disturbed outgrowth pattern into the host iris as compared to the control group. Furthermore, the outgrowth area and axon bundle formation was significantly greater in the control group than in the ethanol group. Electrophysiological recordings revealed a dose-dependent biphasic effect of locally applied ethanol on transplanted monoaminergic neurons. Low doses of ethanol (0.5-3 mM) induced an increase in basal firing rate of control neurons, while higher doses (10-100 mM) caused inhibition. However, monoaminergic neurons in the ethanol group showed a decreased neuronal sensitivity to locally applied ethanol. The same dose of locally applied ethanol which produced an excitation of neuronal activity in the ethanol transplants produced an inhibition in the control grafts. The dose-response curve was shifted to the right. The present results suggest that chronic ethanol exposure during early development leads to altered axonal outgrowth from brainstem 5-HT neurons, as well as decreased sensitivity of these neurons to locally applied ethanol.

Effect of acute ethanol exposure during pregnancy on dentate gyrus synaptic plasticity in 45-day-old rats

Pregnant Wistar rats were treated during the eighth day of gestation (GD8) with two IP injections, spaced by an interval of 4 h, of either ethanol (2.9 g/kg in saline solution) or saline. At 45 days of age, rats prenatally exposed to alcohol showed an improved hippocampal synaptic plasticity in granule cells layer of dentate gyrus. This was assessed measuring the threshold to generate long-term potentiation (LTP) on hippocampal slices. We propose that this result might account for the good performance in some learning tasks observed in animals prenatally exposed to alcohol during short periods.

Ethanol exposure affects trophic factor activity and responsiveness in chick embryo

Chick embryos were chronically exposed to either ethanol (approximately 30 mg/d) or saline, from E4-E13. Homogenate extract was prepared from forebrain tissue from E16 experimental and control embryos and was applied to cultured dorsal root ganglia (DRG). Neurotrophic activity in the forebrain extract (FBX) was significantly reduced in the ethanol-treated embryos compared to saline controls, both in terms of influences on neuronal survival and process elaboration. In addition, E8-9 DRGs from embryos exposed to ethanol from E4 were less viable in the presence of NGF than were those from controls. DRG survival in the presence of E16 FBX (from untreated embryos) was not different following ethanol treatment, but neurite production was significantly reduced. These results suggest that neurotrophic factor content and responsiveness may be appreciably altered following chronic prenatal ethanol exposure. Such alteration could underlie certain CNS anomalies seen in the fetal alcohol syndrome.

Delayed thermoregulatory changes in the immature rat following a single injection of ethanol

Adult rats exhibit rebound hyperthermia within 24 hr following a single injection of ethanol (EtOH). Tests were conducted to determine whether similar changes in thermoregulatory ability occur in the immature rat. Animals were administered saline or EtOH (4 g/kg BW; intraperitoneally) at 2 to 3, 8 to 9, or 14 to 15 days of age. Littermates were handled or left undisturbed with the dams to serve as controls. All rats were tested at 24 or 48 hr post-treatment to measure steady-state colonic temperature (Tco), tail skin temperature and metabolic rate (MR) at both thermoneutral and cold ambient temperatures (Tas). The youngest group exhibited no delayed change in body temperature or MR at 24 or 48 hr post-treatment with EtOH. Likewise, thermoregulatory ability of rats pretreated with EtOH at 8 or 9 or 14 to 15 days of age was not significantly different from controls when tested 24 hr post-treatment at thermoneutral Ta. In contrast, Tco of EtOH-treated rats in the two older age groups was 1 degree C above control level when tested 24 hr post-treatment at cold Ta. This Tco response can be explained by differences in heat transfer to the tail and MR. No altered response to cold Ta was found at 48 hr postinjection, indicating recovery from the EtOH effect. A single injection with EtOH at 2 to 15 days of age results in a change in Tco, which is dependent on postinjection time, age, and Ta.

Sexual receptivity of adult female rats prenatally intoxicated with alcohol on gestational day 8

On gestational day 8 (GD 8), pregnant albino rats received two IP injections, spaced by 4 hours, of either ethanol (2.9 g/kg in 24% v/v saline solution) or saline. Adult females exposed to ethanol in utero showed greater sensitivity to estrogen, but not to estrogen plus progesterone, for induction of lordotic response. The 5-HT1 receptor agonist 5-methoxy-N,N-dimethyl-tryptamine (5-MeODMT) had a significantly smaller effect in inhibiting lordosis response in experimental rats. The greater sensitivity to estrogen and lower sensitivity to the receptor agonist could be a consequence of long-term changes in central neurotransmitter systems induced by acute intoxication with ethanol on GD 8.

Neonatal alcohol exposure alters suckling behavior in neonatal rat pups

Prenatal alcohol exposure has been associated with a variety of suckling deficits in both humans and animals. In this study, the effect of neonatal alcohol exposure on suckling performance was examined in 15-day-old rat pups. Neonatal alcohol exposure has been used as a model to study the effects of alcohol exposure during a period equivalent to the human third trimester with respect to brain growth. Subjects were Long-Evans rats which had been artificially reared (AR) and fed through gastrostomy tubes from postnatal day (PN) 4-PN 12. The AR groups included two groups given ethanol doses of 6 g/kg/day or 4 g/kg/day and an isocaloric maltose-dextrin control group. A suckled control group raised by their natural mothers was also included to control for artificial rearing. Fifteen-day-old pups were individually placed with an anesthetized dam for a 1-h videotaped test session. Pups in the 6 g/kg alcohol group took longer to attach to the nipple and spent less time suckling than pups from all other treatment groups. Nipple-shifting behavior was disrupted in all artificially reared groups, but it was most severely affected in the 6 g/kg group. These findings suggest that neonatal alcohol exposure interferes with suckling performance and these altered behaviors may contribute to the postnatal growth deficits that have been reported following alcohol exposure in utero.

Effects of prenatal alcohol on gamma-glutamyl transpeptidase in various brain regions

Prenatal exposure of rats to alcohol produces morphological, biochemical, behavioral and physiological abnormalities. The enzyme gamma-glutamyl transpeptidase activity is increased when an animal is exposed to alcohol chronically. We examined the effect of the in utero exposure to alcohol on the regional brain distribution of gamma-GTP. Pregnant rats were placed into the following treatment groups: LC (ad lib lab chow and water), PF (pair-fed), 10% EDC (ethanol derived calories), 20% EDC and 35% EDC. The LC group was fed lab chow and water ad lib, the PF, 10% EDC, 20% EDC and 35% EDC groups were fed a liquid diet containing either 0%, 2%, 4% or 6.7% v/v ethanol, respectively. All the treatment groups received the same volume of an isocaloric diet as was consumed by the 35% EDC group. At birth, litters were culled to six and cross fostered to untreated surrogate mothers. Pups were sacrificed at 30 days of age and brains dissected into 8 regions. Each brain region was homogenized and divided into soluble and membrane bound fractions by centrifugation and digestion with deoxycholic acid. gamma-GTP activity was then measured. It was determined that the in utero exposure to alcohol produces an increase in brain gamma-GTP activity. The increase in gamma-GTP activity in some areas of brain is maintained at least until the animals are 30 days old. Alcohol treatment had no effect on the activity associated with the soluble form of enzyme. However, the activity associated with the membrane bound form of the enzyme was increased in several brain regions.(ABSTRACT TRUNCATED AT 250 WORDS)

Response to an ethanol challenge dose on sleep time and blood alcohol level in Wistar rats prenatally exposed to ethanol during gestational day 8

Pregnant albino rats were treated during the eighth day of gestation (GD 8), with two IP injections, spaced by 4 hours, of either ethanol (2.9 g/kg in 24% v/v saline solution) or saline. Maternal blood alcohol levels reached a peak of 457 mg/dl 60 min after the second dose. At the age of 45 days, an equal number of male and female offspring were injected with 3.5 g/kg ethanol and sleep time and blood ethanol levels were determined upon awakening. Ethanol metabolic rate was studied in other individuals injected with the same dose of ethanol and the slope of the linear descending portion of the curves was calculated. Animals that received ethanol in utero exhibited shorter sleep time and higher blood ethanol levels at the moment of awakening than controls. The rate of ethanol metabolism was similar in both groups. These results show that an acute intoxication with ethanol during GD 8 induced long-term changes in the CNS of offspring which caused reduced sensitivity to ethanol hypnotic effects.

Alterations in regional catecholamine content and turnover in the male rat brain in response to in utero ethanol exposure

Fetal ethanol exposure is known to produce CNS abnormalities. The molecular basis for these manifestations observed in animals exposed to ethanol in utero may be explained by changes in regional catecholamine content and turnover. This study was designed to determine changes in catecholamine content and turnover in the cerebral cortex, cerebellum, medial basal hypothalamus, diencephalon, and septal area of male rats exposed to ethanol pre- and postnatally. Pregnant Sprague-Dawley rats were exposed to either an ad libitum liquid diet containing 35% ethanol-derived calories, an isocalorically matched liquid diet, or a diet consisting of laboratory chow and water. Regional alterations in catecholamine content and turnover in each of the brain areas were observed on postnatal Day 18. A regional variability was demonstrated in the effect of in utero ethanol exposure on catecholamine content and turnover. The most dramatic effect was found in the dopaminergic neurons of the medial basal hypothalamus where in utero ethanol exposed offspring had a significantly reduced DA content and turnover when compared to pups from both isocalorically matched and chow-fed dams. These data indicate that the dopaminergic neurons of this particular brain region are susceptible to alteration by ethanol exposure during development and that this alteration cannot be explained by changes in nutrition alone.

Impaired spatial navigation in adult female but not adult male rats exposed to alcohol during the brain growth spurt

Two groups of male and female rats were given the same dose of alcohol using an artificial rearing procedure on postnatal days 4-10. One group received the alcohol in a condensed manner each day which caused cyclic blood alcohol concentrations (BACs) with high peaks. A second group received the alcohol in a uniform manner over each day which resulted in moderate, stable BACs. Two control groups consisted of male and female rats artificially reared but not exposed to alcohol and rats reared normally by dams. All rats were raised to 90 days of age and then tested for spatial navigation ability in the Morris water maze, which involved locating a hidden underwater platform using distal extramaze cues. Neither the alcohol treatments nor the artificial rearing had any effects on performance of adult male rats relative to suckle controls in this task. In contrast, the condensed alcohol exposure but not the uniform alcohol exposure resulted in detrimental performance in the Morris water maze by adult female rats. When the ability to locate and escape onto a visible platform was examined, there were no differences between the female groups given condensed alcohol exposure or artificially reared on milk solution alone. Thus, exposure to high BACs during the brain growth spurt has a lasting and selective detrimental effect on spatial navigation learning in adult female but not adult male rats.

Neurochemical, but not behavioral, deviations in the offspring of rats following prenatal or paternal inhalation exposure to ethanol

In addition to its widespread social use, ethanol is used extensively as an industrial solvent. Inhalation exposures to ethanol which produce narcosis in maternal rats are not teratogenic. The present study sought to extend the previous research by including offspring from paternal exposures, and testing for behavioral disorders in the offspring following maternal or paternal exposures. Groups of 18 male (approximately 450 g) and 15 female (200-300 g) Sprague-Dawley rats were exposed 7 hours/day for six weeks or throughout gestation to 16000, 10000, or 0 ppm ethanol by inhalation and then mated with untreated rats. Litters were culled to 4 males and 4 females, and were fostered within 16 hours after birth to untreated dams which had delivered their litters within 48 hours previously. Offspring from paternally or maternally exposed animals performed as well as controls on days 10-90 in tests of neuromotor coordination (ascent on a wire mesh screen, rotorod), activity levels (open field, modified-automated open field, and running wheel), and learning ability (avoidance conditioning and operant conditioning). In addition, brains of 10 21-day-old pups were analyzed for neurochemical differences from controls in concentrations of protein and the neurotransmitters acetylcholine, dopamine, norepinephrine, 5-hydroxytryptamine, substance P, Met-enkephalin, and beta-endorphin. Levels of acetylcholine, dopamine, substance P, and beta-endorphin were essentially unchanged in the offspring of rats exposed to ethanol. Complex, but significant changes in levels of norepinephrine occurred only in paternally exposed offspring. 5-Hydroxytryptamine levels were reduced in the cerebrum, and Met-enkephalin levels were increased in all brain regions of offspring from both maternally and paternally exposed rats.

Alterations of fetal brain biogenic amine metabolites by maternal ethanol exposure

1. Pregnant Sprague-Dawley rats treated chronically with ethanol (3 g/kg daily for the last third of pregnancy) had decreased placental weights at birth (ca 23%). 2. Whole fetal brain levels of HVA and 5-HIAA were similarly decreased 32 and 38%, respectively. 3. MHPG levels were also marginally reduced (i.e. 15% decline). 4. In the presence of a potent type A MAO inhibitor (harmaline, 10 mg/kg maternal weight 2 hr before fetal delivery) co-treatment with ethanol was found to result in a 60% elevation of whole fetal brain norepinephrine levels. 5. Other biogenic amines and metabolites were not altered by ethanol treatment.

Effects of physostigmine on shuttle avoidance in rats exposed prenatally to ethanol

Shuttle avoidance performance following pretreatment with physostigmine was assessed in 85- to 100-day-old rats whose mothers consumed a liquid diet consisting of 35% ethanol-derived calories (EDC) during pregnancy. Offspring of pair-fed (0% EDC) and ad lib lab chow (LC) dams served as controls. Animals received either 0, 0.1 or 0.2 mg/kg physostigmine sulfate prior to acquisition training in a shuttle avoidance apparatus. Training consisted of 50 trials/day for 4 days. Thirty-five percent EDC rats made fewer avoidances than controls during acquisition training. Treatment with physostigmine reduced the number of avoidances made, and did so similarly for all prenatal treatment groups. Escape latencies were not affected by prenatal treatment, although they were increased by physostigmine administration prior to training. Neither prenatal treatment nor physostigmine treatment affected activity as measured by the number of intertrial crossings while in the apparatus. These data indicate that alcohol-exposed animals did not respond differentially to physostigmine relative to controls, suggesting that cholinergic dysfunction may not underlie the prenatal alcohol-induced deficit in active avoidance.

Neurotransmitter glutamate: its clinical importance

Excitatory amino acid glutamate has several important functions in the mammalian central nervous system (CNS). This review focuses on the transmitter role of glutamate and discusses anatomical and pharmacological data of clinical neurological relevance. Experimental and clinical conditions which have been associated with altered content, uptake, membrane binding or release of glutamate in the CNS are discussed. Such conditions include, epilepsy, disorders of the basal ganglia, cerebral ischemia, hypoxia, hypoglycemia, metabolic encephalopathies, olivopontocerebellar atrophy and cerebellar ataxias, amino acidopathies, mental and other neurological disorders. With the exception of a few fibre systems, it is very difficult to differentiate between glutamate and aspartate as CNS transmitters. The term glutamate is, thus, used in the sense glutamate and/or aspartate unless specifically stated.

Prenatal ethanol and ontogeny of pituitary-adrenal responses to ethanol and morphine

The development of pituitary-adrenal activity was examined in the offspring of rat dams fed a 5.0% w/v ethanol-containing liquid diet or pair-fed an isocaloric diet, as a nutritional control, from day 8 of gestation to parturition. Serum corticosterone responses of the pups to challenges with ethanol (1.5 g/kg) or morphine (3.0 mg/kg) were determined at 5, 7, 10, 12 and 18 days of age. The pituitary-adrenal axis of normal neonates was activated by the drugs at each age, with a characteristic biphasic developmental pattern in which a trough occurred at day 7. The overall pattern was unaffected by prenatal ethanol exposure or pair-feeding. However, both prenatal treatments intensified the trough. Already on day 5 and also on day 7, corticosterone responses of both the ethanol-exposed and pair-fed offspring to ethanol were significantly lower than responses of normal pups. Additionally, on day 7, ethanol-exposed offspring had significantly lower responses to ethanol than pair-fed offspring and significantly lower responses to morphine than normal pups. Thus, both the prenatal ethanol and pair-feeding treatments suppressed pituitary-adrenal responsiveness of 5 and 7 day-old neonates to the drug challenges. This is in marked contrast to our previous findings for adult prenatally ethanol-exposed offspring whose pituitary-adrenal responses to the same drugs, as well as to other stressors, are consistently enhanced in comparison to pair-fed derived rats, whose responses in adulthood no longer differ from normals.

Prenatal antiepileptic drug exposure alters seizure susceptibility in rats

An animal model is used to address the issue of prenatal exposure to certain antiepileptic drugs and seizure susceptibility in the offspring. Administration of doses established as median therapeutic doses in humans of phenobarbital, valproate and clonazepam to pregnant rats during the last third of gestation produced sexually dimorphic alterations in pentylenetetrazol (PTZ)-induced seizures as well as in non-convulsive (spontaneous alternation and cliff avoidance) behaviors in the offspring. Altered seizure susceptibility occurred in the absence of overtly recognizable morphological abnormalities and did not appear to reflect differences in the status of circulating drug-binding plasma proteins. Possible neural and/or metabolic mechanisms responsible for these behavioral changes are discussed.

Suckling deficits in rat pups exposed to alcohol in utero

With the aid of a pair-feeding procedure, two groups of pregnant Long-Evans rats were fed a liquid diet containing 35% or 0% ethanol-derived calories during days 6-20 of gestation. A third group was allowed free access to standard lab chow and water throughout pregnancy. At 6-7 or 9-10 days of age, suckling performance by male and female offspring representing the three prenatal treatment groups was examined. The test stimulus was a 6-10-day postparturient, anesthetized dam in which milk letdown was prevented. Compared to both pair-fed and lab chow controls, alcohol-exposed animals exerted a lower maximum suckling pressure, spent less time suckling during the test session, and displayed an altered suckling pattern. These data are consistent with existing clinical and experimental evidence documenting sucking deficits following prenatal alcohol exposure and are discussed in terms of prenatal alcohol-induced CNS impairment.

Lactational ethanol exposure: brain enzymes and [3H]spiroperidol binding

Long-Evans lactating rats were fed 27% calories as ethanol in a liquid diet to determine whether alcohol received through the milk would alter normal brain development in the offspring. On days 16, 21 and 30, brains of the female offspring were removed, corpus striatum dissected and assayed for choline acetyltransferase activity, glutamic acid decarboxylase activity and [3H]spiroperidol binding activity. At day 16, there were no differences among the three treatment groups for the enzyme activities assayed. At day 21, glutamic acid decarboxylase activity in the pairfed group was higher than in ET and CT groups. Choline acetyltransferase activity in PF group was higher when compared to ad libitum controls and [3H]spiroperidol binding was not affected. At 30 days of age, animals exposed to ethanol had higher choline acetyltransferase activity and [3H]spiroperidol binding activity when compared to pairfed and ad libitum controls; and higher glutamic acid decarboxylase activity when compared to ad libitum controls. Data from the present study suggest that ethanol exposure during the brain growth spurt has a toxic effect on the late development of dopaminergic, cholinergic and GABAergic systems in the corpus striatum. These results may be related to the clinical symptoms of hyperactivity and problems with motor control in children exposed to alcohol during the third trimester and during lactation.

The effects of physostigmine on open-field behavior in rats exposed to alcohol prenatally

The present study examined the effects of physostigmine, a cholinesterase inhibitor, on activity in young rats whose mothers consumed isocaloric liquid diets containing 35% or 0% ethanol-derived calories on days 6-20 of pregnancy. A pair-feeding procedure was utilized and an ad libitum lab chow group was included. Physostigmine was administered to 18-day-old offspring on 3 consecutive days with activity measures recorded for 30 min each day. Injections of physostigmine produced significant reductions in activity in alcohol-exposed offspring relative to control groups. These results provide support for a functional cholinergic deficit in offspring exposed to alcohol in utero and may have relevant clinical implications in the treatment of attentional deficit disorder which can occur following prenatal alcohol exposure.