Ethanol-exposed Rats Research Articles

Prenatal ethanol exposure alters the expression of period genes governing the circadian function of β‐endorphin neurons in the hypothalamus

Sleep-wake disturbances and stress hyper-responsiveness have been observed in human neonates, children and adolescents who were exposed to alcohol during the prenatal period. Using the laboratory rat as an animal model, we investigated whether fetal ethanol exposure during gestational days 10-21 affects the circadian function of the stress-axis regulatory beta-endorphin neurons in the hypothalamus. Fetal ethanol-exposed rats showed abnormality in the circadian expression of proopiomelanocortin (POMC) mRNA encoding the peptide beta-endorphin in the arcuate nucleus of the hypothalamus during the adult period. These rats also showed altered circadian expression of the clock governing Period genes rPer1, rPer2 and rPer3, in the arcuate nucleus, and rPer1 and rPer 2 mRNA levels in the suprachiasmatic nucleus. Laser captured microdissection analysis identified constitutive expression of rPer1, rPer2 and rPer3 genes in beta-endorphin-containing neurons. These data suggest for the first time that fetal exposure to ethanol significantly alters the clock mechanisms governing the circadian function of beta-endorphin neurons.

Effect of lecithin in the treatment of ethanol mediated free radical induced hepatotoxicity

Alcoholic liver disease (ALD) develops as a consequence of priming and sensitizing mechanisms rendered by cross-interactions of primary mechanistic factors and secondary risk factors. Liver damage due to consumption of alcohol may be caused by oxygen radicals such as superoxide and hydroxyl radicals, generated during the metabolism of ethanol by the microsomal oxidizing system. Lecithin, an important class of phospholipids contains choline, which is considered as lipotropic factor. The effects of this lecithin as a hepatoprotective drug on body weight and antioxidant status of ethanol-exposed rats were studied. The results were compared with the effects of tocopheryl acetate. From the present study, it can be concluded that ethanol-induced stress can be partly prevented by tocopheryl acetate, and showed best result. Abstination from alcohol also involved for little hepatic regeneration. Supplementation of lecithin showed better effect compared to abstination from alcohol on reversing the effect of ethanol induced liver damage in the present study. Moreover, preventive measures were found to be better than curative treatment. Antioxidants are likely to provide beneficial effects on hepatocyes via desensitization against oxidant stress while inhibiting primary mechanism for expression of proinflammatory and cytotoxic mediators. However, abstinence from alcohol, proper nutrition, and supplementation of antioxidants, vitamins and hepatoprotective drugs are some of the therapeutic options.

Reestablishing an Intragastric Ethanol Self‐infusion Model in Rats

There is a scarcity of behavioral models that will reliably produce ethanol intakes in rodents at levels that induce or maintain dependence. The present experiments were designed to reestablish a model that uses passive intragastric (IG) infusion of ethanol to induce tolerance/dependence/withdrawal before allowing rats to self-infuse ethanol intragastrically. Sprague-Dawley rats were surgically implanted with IG catheters and allowed to recover. During the passive infusion phase (3-6 days), rats in the experimental group were passively infused with 10% (v/v) ethanol (3.3-12.2 g/kg/d). Rats in the control group were not infused. During the self-infusion phase (5-6 days), all rats had access to 2 flavored solutions. Licks on 1 solution were paired with ethanol infusions (20%, v/v) whereas licks on the other solution were unpaired. Experiments differed in the specific passive infusion parameters and in the ethanol intake limit during self-infusion. Rats in the experimental groups self-infused more ethanol per day (means of 4-7 g/kg/d) than did rats in the control group (means of 0-2.6 g/kg/d). Across all 3 studies, individual total daily intakes exceeded 5 g/kg on 35% of the self-infusion days in ethanol-preexposed rats compared with <1% of the self-infusion days in the control rats. Ethanol-exposed rats also infused a substantially higher percentage (42%) of their total ethanol intake in relatively large bouts (>1.5 g/kg) compared with control rats (<10%). The addition of a daily 6-hour ethanol-free period during the passive infusion phase (in Experiments 2 and 3) led to higher ethanol intakes than in Experiment 1. Results of a control experiment showed that differences between experimental and control groups in Experiments 1 to 3 were a result of ethanol experience and not a general effect of differential infusion experience. Relatively short periods of passive IG infusion of ethanol induced levels of ethanol self-infusion in genetically heterogeneous rats that were comparable with drinking intakes previously reported in rats selectively bred for ethanol intake/preference. Although the induction of dependence/withdrawal may have played a role in this outcome, an alternative interpretation is that experimental rats self-infused more ethanol because passive exposure produced tolerance to aversive pharmacological effects that would otherwise limit intake of the paired flavor because of development of conditioned taste aversion. The current findings provide a strong basis for future work designed to identify parametric determinants of this form of self-administration, its sensitivity to genetic influences, and its neurobiological substrates.

Ethanol exposure during development reduces resident aggression and testosterone in rats

Ethanol exposure during development has been shown to alter social behaviors in people, but the range of deficits is not clear. Using an animal model of Fetal Alcohol Spectrum Disorders, inter-male aggression and testosterone levels were examined in adult rats. Rats were exposed to ethanol during the entire prenatal period and from postnatal day 2 through 10. Ethanol was administered via intragastric intubation. Two other groups consisted of a nontreated control and an intubated control group that was exposed to the administration procedures but not ethanol. Both offensive and defensive aggression were examined in experimental residents and intruders under three different housing conditions for the resident males: (1) with another male, (2) with a pregnant female, and (3) with a female and litter fathered by the experimental animal. When housed with a female and litter, ethanol-exposed rats displayed reduced offensive aggression compared to control groups under the same condition. Defensive aggression in the non-experimental intruders was reduced in this same condition. There were no differences in duration of non-aggressive social behaviors among the groups in any of the housing conditions. Testosterone levels were reduced in ethanol-exposed rats compared to controls. In summary, ethanol exposure over the combined prenatal and postnatal periods reduces aggressive behavior in a condition where aggressive behavior is normally seen. This reduction may be related to lower testosterone levels.

Enhanced Prepulse Inhibition Following Adolescent Ethanol Exposure in Sprague-Dawley Rats

Recent studies have demonstrated that ethanol exposure differentially affects adolescents and adults. The current studies were designed to compare the effects of 2-week exposure to ethanol during adolescence or adulthood on the acoustic startle response (ASR) and prepulse inhibition (PPI) METHODS: Male Sprague-Dawley rats were exposed to ethanol vapor 12 hr/d (on from 6 pm to 6 am) for 14 days during adolescence or adulthood. Six days after the cessation of ethanol vapor exposure, the ASR and PPI were assessed. During ethanol treatment, overall blood alcohol levels averaged 230 to 250 mg/dl in the adolescent and adult treatment groups. Assessment of the ASR revealed that latency to startle was more rapid in adolescents than in adults, but ASR latency was not altered by ethanol exposure. In addition, ASR magnitude was lower in adolescents and was decreased in ethanol-exposed rats on startle trials. Ethanol exposure significantly enhanced PPI, but only after adolescent exposure These data further demonstrate a differential sensitivity of adolescents and adults to the effects of ethanol exposure. Specifically, a 2-week period of ethanol exposure during adolescence selectively enhanced PPI, a neurobehavioral index of sensorimotor gating. However, ASR magnitude was decreased by ethanol exposure regardless of age. On the basis of previous studies, the effects of ethanol exposure on PPI data could indicate that adolescent rats exposed to ethanol are more likely to exhibit behavioral inflexibility and that ethanol exposure acts as a more potent physical stressor in adolescent rats.

Effect of Chronic Ethanol Ingestion and Gender on Heart Left Ventricular p53 Gene Expression

Although the beneficial effects of mild to moderate ethanol consumption have been implied with respect to heart, alcohol abuse has proven to be a major cause of nonischemic cardiomyopathy in Western society. However, the biochemical and molecular mechanisms, which mediate the pathologic cardiac effects of ethanol, remain largely unknown. The aim of the present study was to explore the effects of chronic ethanol exposure on cardiac apoptosis and expression of some of the genes associated with cardiac remodeling in vivo. Alcohol-avoiding Alko Non Alcohol rats of both sexes were used. The ethanol-exposed rats (females, n=6; males, n=8) were given 12% (v/v) ethanol as the only available fluid from age of three to 24 months of age. The control rats (females, n=7; males, n=5) had only water available. At the end of the experiment, free walls of left ventricles of hearts were immediately frozen. Cytosolic DNA fragmentation, reflecting apoptosis, was measured using a commercial quantitative sandwich enzyme-linked immunosorbent assay kit, and mRNA levels were analyzed using a quantitative reverse transcriptase-polymerase chain reaction method. Ethanol treatment for two years increased cardiac left ventricular p53 mRNA levels significantly (p=0.014) compared with control rats. The gene expression was also dependent on the gender (p=0.001), so that male rats had higher left ventricular p53 mRNA levels than female rats. However, no significant differences in levels of DNA fragmentation were detected. Chronic ethanol exposure in vivo induces rat cardiac left ventricular p53 gene expression. Expression of p53 is also gender-dependent, males having higher p53 mRNA levels than females. This preliminary finding suggests a role for the p53 gene in ethanol-induced cardiac remodeling. The results might also have some relevance for the known gender-dependent differences in propensity to cardiovascular disease.

Systemic ethanol administration elevates deoxycorticosterone levels and chronic ethanol exposure attenuates this response

Systemic ethanol administration is known to elevate levels of the GABAergic neuroactive steroid 3α,21-dihydroxy-5α-pregnan-20-one (3α,5α-THDOC). 3α,5α-THDOC is synthesized from deoxycorticosterone (DOC) by metabolism in adrenals and brain. The present study investigated DOC levels in plasma and brain following ethanol administration to naïve and ethanol-exposed rats. Rats were administered ethanol (2 g/kg, i.p.) or saline and DOC levels were measured in plasma and brain regions by radioimmunoassay. Chronic ethanol-exposed rats were administered an ethanol challenge (2 g/kg, i.p.) following 15 days of ethanol liquid diet consumption. Ethanol administration markedly increased DOC levels in plasma, cerebral cortex, hippocampus, hypothalamus, cerebellum, and olfactory tubercle of naïve rats. Ethanol challenge produced an attenuated elevation of DOC in rat plasma and brain following chronic ethanol consumption for 2 weeks. These findings suggest that acute ethanol increases DOC levels in ethanol naïve rats and chronic ethanol consumption induces tolerance to ethanol-induced increases in DOC levels.

Short-Term Memory Impairment and Reduced Hippocampal c-Fos Expression in an Animal Model of Fetal Alcohol Syndrome

Previous work in our laboratory has shown that exposure to ethanol during the brain growth spurt impairs spatial short-term memory in rats on the delayed matching-to-place (DMP) version of the Morris water maze. The objectives of this study were to ascertain whether this impairment could: 1) be prevented by increasing the length of encoding time and 2) be related to hippocampal c-Fos expression. Using an artificial rearing model, male Long-Evans rats were fed 6.5 g/Kg/day of ethanol from postnatal days 6-9, with controls fed an isocaloric amount of maltose dextrin. As adults, rats in each treatment condition were trained and subsequently tested on either the DMP version of the Morris water maze, or on a random platform version (RAN) that incorporated the same performance requirements, but disallowed spatial learning. Brains were processed for c-Fos expression. Ethanol-exposed rats showed longer search trials during training and took longer to learn the DMP task. When the delay between search and recall trials was increased from 60 sec to 120 min, the performance of ethanol-exposed rats was impaired compared with that of controls after a 10 sec, but not after a 45 sec, encoding time. Brain c-Fos expression was increased in hippocampus, prefrontal cortex and visual cortex in rats trained on the DMP compared to the RAN task. Furthermore, in the DMP-trained rats, hippocampal c-Fos expression was lower in ethanol-exposed rats. These results suggest that the short-term memory impairment of ethanol-exposed rats 1) can be improved slightly by an increase in encoding time and 2) is related to a decrease in c-Fos expression in the hippocampus.

Fetal Alcohol Effects: Potential Treatments From Basic Science

This article represents the proceedings of a symposium presented at the 2004 annual meeting of the International Society for Biomedical Research on Alcoholism, held in Mannheim, Germany. The presentations were as follows: 1) “Antioxidants Prevent Ethanol-Induced Cell Death in Developing Brain and in Cultured Neural Cells” by M. Pascual, M. C. García-Minguillán, and Consuelo Guerri; 2) “Rational Development of Ethanol Antagonists” by Michael E. Charness and Michael F. Wilkemeyer; 3) “Choline Supplementation as a Treatment for Fetal Alcohol Effects” by Jennifer D. Thomas and Hector D. Dominguez; 4) “Cerebellar and Cortical Plasticity After Neonatal Alcohol Exposure: Model of Intervention” by Anna Y. Klintsova, Charles R. Goodlett, and William T. Greenough; and 5) “Circadian Rhythms in Prenatally Ethanol-Exposed Rats” by Hiromi Sakata-Haga.

Prenatal Alcohol Exposure Causes Attention Deficits in Male Rats.

Children with fetal alcohol spectrum disorder (FASD) are often diagnosed with attention-deficit/ hyperactivity disorder (ADHD). These children show increases in reaction time (RT) variability and false alarms on choice reaction time (CRT) tasks. In this study, adult rats prenatally exposed to ethanol were trained to perform a CRT task. An analysis of the distribution of RTs obtained from the CRT task found that rats with a history of prenatal ethanol exposure had more variable RT distributions, possibly because of lapses of attention. In addition, it was found that, similar to children with FASD, the ethanol-exposed rats had more false alarms. Thus, rats with prenatal ethanol exposure show attention deficits that are similar to those of children with FASD and ADHD.

The effects of ethanol on the developing cerebellum and eyeblink classical conditioning

In rats, developmental ethanol exposure has been used to model the central nervous system deficits associated with human fetal alcohol syndrome. Binge-like ethanol exposure of neonatal rats depletes cells in the cerebellum, including Purkinje cells, granule cells, and deep nuclear cells, and produces deficits in simple tests of motor coordination. However, the extent to which anatomical damage is related to behavioral deficits has been difficult to estimate. Eyeblink classical conditioning is known to engage a discrete brain stem-cerebellar circuit, making it an ideal test of cerebellar functional integrity after developmental ethanol exposure. Eyeblink conditioning is a simple form of motor learning in which a neutral stimulus (such as a tone) comes to elicit an eyeblink when repeatedly paired with a stimulus that evokes an eyeblink prior to training (such as mild periorbital stimulation). In eyeblink conditioning, one of the deep cerebellar nuclei, the interpositus nucleus, as well as specific Purkinje cell populations, are sites of convergence for tone conditioned stimulus and somatosensory unconditioned stimulus information, and, together with brain stem nuclei, provide the necessary and sufficient substrate for the learned response. A series of studies have shown that eyeblink conditioning is impaired in both weanling and adult rats given binge-like exposure to ethanol as neonates. In addition, interpositus nucleus neurons from ethanol-exposed rats showed impaired activation during eyeblink conditioning. These deficits are accompanied by a permanent reduction In the deep cerebellar nuclear cell population. Because particular cerebellar cell populations are utilized in well-defined ways during eyeblink conditioning, conclusions regarding the underlying neural substrates of behavioral change after developmental ethanol exposure are greatly strengthened.

Neurophysiologic consequences of neonatal ethanol exposure in the rat

Many of the neurotoxic and neurobehavioral consequences of neonatal ethanol exposure in the rat have been characterized. However, in few studies has adult neurophysiologic function been assessed in rats exposed to ethanol during this key developmental period. In the current study, the effects of neonatal ethanol exposure on adult electroencephalographic (EEG) activity and auditory event-related potentials (ERPs) were examined in the rat. Male Sprague–Dawley rats were exposed to ethanol at 6.0 g/kg/day between postnatal days 4 through 9 by using an artificial-rearing procedure. Two control groups were used: a suckle control (SC) group and a gastrostomized control (GC) group. After reaching adulthood (i.e., at 3.5–4 months old), recording electrodes were implanted into the brain of each rat, so that EEG activity and auditory ERPs from the cortex and hippocampus could be assessed. Rats exposed to ethanol during the neonatal period were hyperactive as adults. Assessment of the EEG activity revealed that ethanol exposure increased peak frequency in the frontal cortical and parietal cortical 16–32 Hz frequency bands. Assessment of ERPs revealed that parietal cortical N1 amplitude was reduced in ethanol-exposed rats. Furthermore, parietal cortical N1 latency was increased in the GC group. These findings demonstrate that enhanced motor activity in rats exposed to ethanol during neonatal development occurs in combination with EEG indices of enhanced cortical and hippocampal arousal. Furthermore, a deficiency in cortical N1 amplitude indicates adult rats may have attention deficits. Overall, these results indicate that neonatal ethanol exposure has enduring neurobehavioral consequences, which persist into adulthood. This neurobehavioral profile in the rat is consistent with clinical observations of attention deficits and hyperactivity in children exposed to ethanol during prenatal development.

Hydrocephalus following prenatal exposure to ethanol.

Pregnant rats were administered a liquid diet containing 5% (w/v) ethanol between gestational days 10 and 21, and the brains of nine offspring were examined at 8 weeks of age. Two ethanol-treated offspring showed obvious hydrocephalus characterized by markedly enlarged lateral ventricles. Most of the other ethanol-treated rats only showed a slight enlargement of the lateral ventricles. An ethanol-treated offspring showed no neuropathological signs of hydrocephalus. Histological observation of the hydrocephalic brains revealed dilation of the lateral ventricles, loosely bundled corpus callosum, hypoplasia of the septum and fimbria, and thinning of the cerebral cortices. There were no differences in the shape of the third ventricle and aqueduct between hydrocephalic and non-hydrocephalic rats. Ectopic cell clusters were found on the surface of the lateral ventricle and in the interventricular foramen in ethanol-treated rats with hydrocephalus. However, leptomeningeal heterotopias were found on the cortical surface in ethanol-exposed rats independently of whether or not they showed hydrocephalus. Thus, heterotopias within the ventricles may be related to the genesis of hydrocephalus following prenatal ethanol exposure. However, whether they could be a direct cause of the hydrocephalus is uncertain as they seem to be not enough large to block the current of the cerebrospinal fluid. We also examined the expression of L1, a cell adhesion molecule suspected of involvement in the genesis of hydrocephalus after prenatal ethanol exposure, in 1-day-old rats. Western blot analysis using specific antibody against L1 showed no significant change in L1 protein expression in ethanol-exposed rats. These data suggest that L1 protein expression is not affected by ethanol.

Similar anxiety-like responses in male and female rats exposed to repeated withdrawals from ethanol

Previous research indicated that male rats exhibited anxiety-like behavior following withdrawal from chronic ethanol exposure. This behavior, as well as other symptoms of withdrawal such as seizure susceptibility, may be sensitized in male rats repeatedly withdrawn from chronic ethanol exposure. Because there are sex differences in some alcohol effects, the present study explored whether male and female rats would respond differently to a course of repeated ethanol withdrawals. Similarly aged male and female rats were exposed to a control liquid diet or a diet containing ethanol (7% w/v). Ethanol-exposed rats had only one 5-day cycle of exposure or three cycles, with 2 days of control diet (CD) between cycles. At 5 h after the final ethanol was removed, the rats were placed as same-sexed pairs in the social interaction test; approximately half of the rats were tested later in the elevated plus maze. Rats withdrawn from ethanol after three cycles exhibited reduced the time spent in social interaction and general activity in the social interaction test and reduced the open and closed arm entries in the elevated plus maze. There were no sex differences in these effects. However, male rats exhibited a small anxiety-like response after one cycle of 5 days' exposure to ethanol and female rats did not. Thus, there are no sex differences in the three-cycle multiple-withdrawal paradigm, but there may be differences after briefer exposures.

Effect of prenatal exposure to ethanol on postnatal development of intestinal transport functions in rats.

Alcohol consumption by pregnant animals and humans leads to general growth impairment in their offspring, delayed growth and multiple birth defects collectively called "Fetal Alcohol Syndrome". In utero exposure of ethanol to rat pups causes damage to their developing intestinal epithelium which leads to impairment of nutrient assimilation and growth retardation during postnatal development. To determine the effect of prenatal exposure of ethanol on the postnatal development of rat intestinal Na(+)-dependent and independent D-glucose transporter along with the amino acids (glycine and Lleucine) transporter activity at 4, 8, 14, 20 and 30 days of postnatal age. The changes in the expression levels of Na(+)-dependent glucose transporter (SGLT1) mRNA was assessed at different days of postnatal age in rat pups. Wistar strain albino female rats were fed ethanol at a dose of 2 g/kg body weight/day orally by Ryle's tube for one month before mating and during the entire period of gestation while the control females received isocaloric glucose. Transport studies were performed using the everted intestine of 4, 8, 14, 20 and 30 day-old control and ethanol-exposed pups employing the tissue accumulation method. The expression of SGLT1 mRNA at different days of postnatal age in control and ethanol-exposed rat pups was determined using a Northern Blot analysis. Prenatal exposure of ethanol to rat pups leads to a decrease in their body weight, intestinal length and weight and reduces the uptake capacities of SGLT1 as well as energy dependent glycine and L-leucine transporters with respect to their age-matched controls. However, the mRNA levels of SGLT1 remained unaltered in the ethanol-exposed pups at all ages of postnatal development compared to their controls. These findings suggest that in utero exposure to ethanol leads to a general delay in the postnatal development of the intestine of ethanol-exposed rat pups affecting mainly the development of intestinal energy dependent D-glucose and amino acid (glycine and L-leucine) transporters.

Prenatal exposure to alcohol alters the light response in postnatal circadian rhythm

We studied the effect of prenatal exposure to alcohol on later circadian rhythm in the rat. In the normal light–dark cycle, an 8-h phase advance brought forward the deep body temperature rhythm in control rats, although it had a smaller effect in prenatally ethanol-exposed rats. In long constant darkness, the phase response of the deep body temperature rhythm to a light pulse at the early subjective night was less marked in ethanol-exposed rats in comparison to controls. These results indicate that prenatal exposure to alcohol has a long-lasting effect on the light responsiveness of the deep body temperature circadian rhythm.

Neonatal ethanol exposure produces a hyperalgesia that extends into adolescence, and is associated with increased analgesic and rewarding properties of nicotine in rats.

Drug exposure during CNS development may alter subsequent dependence liability. We postulated that early alcohol exposure might produce persistent alterations in responses to noxious stimuli. Because relief of physical discomfort may be negatively reinforcing, changes in responses to noxious stimuli produced by early alcohol exposure may increase the rewarding properties of nicotine, a potent analgesic. Such factors may contribute to the high level of alcohol and nicotine co-abuse in humans. The purpose of this study was to determine whether neonatal ethanol exposure in rats altered responses to noxious stimuli, and whether nicotine would then be more rewarding to the alcohol-exposed offspring, perhaps via its analgesic actions. Neonatal rats received ethanol by gavage (5.0 or 6.5 g/kg) on postnatal days (PND) 9-13. An iso-caloric control group was also included. Rats were then tested to assess responsiveness to a mild noxious heat stimulus, as measured in the tail-flick assay (PND 14 and PND 28), for their response to acute analgesic injections of either nicotine or ethanol (PND 28), and for nicotine induced conditioned place preference (CPP) (PND 36). Neonatal ethanol exposure produced hyperalgesia during the first 24 h after alcohol withdrawal (PND 14) that continued through PND 28. The analgesic effects of 12.5 microg/kg nicotine were enhanced approximately 2-fold in adolescent rats with previous ethanol histories, relative to controls. These ethanol-exposed rats also showed a significant CPP to nicotine, whereas controls showed no CPP. Persistent decreases in tail-flick response latencies suggestive of hyperalgesia were observed following neonatal ethanol exposure in the rat. These changes were accompanied by increases in the analgesic and place-conditioning effects of nicotine in adolescence. If similar effects occur in humans, prenatal alcohol exposure may play a role in an increased risk for the rewarding effects and dependence liability of nicotine later in life.

Developmental Binge Exposure to Ethanol and Artificial Rearing Do Not Affect the Social Transfer of Diet Preference

Background: A previous study reported no effect of binge exposure to ethanol during the brain growth spurt on the social acquisition of enhanced diet preference in male rats. The objective of this study was to replicate this finding by using the artificial rearing technique and to investigate whether delay‐dependent mnemonic deficits previously observed in the water maze would extend to social memory of diet preference. We also addressed whether this naturalistic behavior was dependent on the presentation of diet odor in the context of a rat‐produced component in ethanol‐exposed rats, as it is in normal controls.Methods: Male rat pups were reared artificially from postnatal days 5 to 18, during which (postnatal days 6–9) they were fed either 6.5 g/kg/day of ethanol in a binge model or an isocaloric maltose‐dextrin solution (gastrostomy controls). A third suckled control group was reared normally. These test rats were allowed to interact with conspecifics that had previously consumed a distinctive diet, X. Subsequently, the experimental rats were provided a choice between two novel diets, one of which was X, after delays of 0 hr (experiment 1), 24 hr, and 4 weeks (experiment 2). In experiment 3, the rats were again given the two‐choice preference test, but after exposure to the diet odor alone.Results: All groups demonstrated a significant preference for the socially cued diet in experiments 1 and 2, and the strength of this inclination remained consistent across the 0‐hr, 24‐hr, and 4‐week retention intervals. Moreover, all groups demonstrated sensitivity to the social context of this task, as shown by a lesser preference for the diet exposed alone in experiment 3.Conclusions: Intact performance on the ethologically meaningful diet‐preference test supports specificity in the cognitive/behavioral effects of developmental exposure to ethanol. Interestingly, early isolation, as experienced in the artificial‐rearing procedure, also did not impair performance on this social task.

Interaction of aging and intermittent ethanol exposure on brain cytochrome c oxidase activity levels

The effects of chronic, intermittent ethanol exposure on brain cytochrome c oxidase (CO) activity levels were studied in young (3- to 4-month-old) and aged (29- to 30-month-old) male Wistar rats. The rats were given highly intoxicating doses of ethanol three times a day by intragastric intubation for four successive days, followed by a 3-day ethanol-withdrawal period. This 4-day ethanol-exposure with 3-day ethanol-withdrawal cycle was repeated five times to simulate the binge drinking of human alcoholics. The histochemical demonstration of CO showed a markedly decreased activity level in the medial prefrontal cortex (especially layer V pyramids and neuropil) of the ethanol-exposed rats of both age groups compared with findings for the respective controls. In the cerebellar vermis, CO activity level was decreased in the Purkinje neurons of the aged ethanol-exposed rats and in the granule cells of both young and aged ethanol-exposed rats. The CO activity level in the locus coeruleus was decreased in both young and old ethanol-exposed rats, but the decrease was more pronounced in the young ethanol-exposed group. Aging per se did not markedly change CO histochemical findings in either prefrontal or cerebellar cortex, but CO activity levels were increased in the locus coeruleus. In summary, results of the current study support our conclusion that CO activity levels were decreased in the cerebral and cerebellar cortices as well as in the locus coeruleus—CNS regions known to be negatively affected by chronic ethanol exposure. Defective energy metabolism due to decreased CO activity levels might compromise neuronal energy stores and thereby contribute to ethanol-induced brain dysfunction and irreversible CNS degeneration.

NMDA receptor subunit expression following early postnatal exposure to ethanol

Changes in NMDA receptor function following early postnatal exposure to ethanol may be related to the expression of NMDA receptor subunits. Following early postnatal exposure to ethanol, the expression of NMDA receptor subunits was examined. In cortex from ethanol-exposed rat pups at postnatal day 21, NR2A was significantly increased. There was no change in NR2B, thus suggesting that ethanol exposure during the third-trimester equivalent produces distinct effects on the NMDA receptor.