Effects of chronic ethanol consumption on pyramidal neurons of the mouse dorsal and ventral hippocampus: a quantitative histological analysis

Oral administration of coenzyme Q10 ameliorates memory impairment induced by nicotine-ethanol abstinence through restoration of biochemical changes in male rat hippocampal tissues

Substance abuse among adolescents has become a growing issue throughout the world. The significance of research on this life period is based on the occurrence of neurobiological changes in adolescent brain which makes the individual more susceptible for risk-taking and impulsive behaviors. Alcohol and nicotine are among the most available drugs of abuse in adolescents. Prolonged consumption of nicotine and alcohol leads to drug dependence and withdrawal which induce various dysfunctions such as memory loss. Coenzyme Q10 (CoQ10) is known to improve learning and memory deficits induced by various pathological conditions such as Diabetes mellitus and Alzheimer's disease. In the present study we investigated whether CoQ10 treatment ameliorates memory loss following a nicotine-ethanol abstinence. Morris water maze and novel object recognition tests were done in male Wistar rats undergone nicotine-ethanol abstinence and the effect of CoQ10 was assessed on at behavioral and biochemical levels. Results indicated that nicotine-ethanol abstinence induces memory dysfunction which is associated with increased oxidative and inflammatory response, reduced cholinergic and neurotrophic function plus elevated Amyloid-B levels in hippocampi. CoQ10 treatment prevented memory deficits and biochemical alterations. Interestingly, this ameliorative effect of CoQ10 was found to be dose-dependent in most experiments and almost equipotential to that of bupropion and naloxone co-administration. CoQ10 treatment could effectively improve memory defects induced by nicotine-ethanol consumption through attenuation of oxidative damage, inflammation, amyloid-B level and enhancement of cholinergic and neurotrophic drive. Further studies are required to assess the unknown side effects and high dose tolerability of the drug in human subjects.

Vitamin B12 administration prevents ethanol-induced learning and memory impairment through re-establishment of the brain oxidant/antioxidant balance, enhancement of BDNF and suppression of GFAP

There are growing evidence indicating that the adolescent brain is persistently affected by the use of psychostimulant agents. In this regard, alcohol drinking has become rather common among the adolescents in many societies during the last decade. It is currently well known that long-term ethanol exposure deteriorates various cognitive functions such as learning and memory. Mechanistically, these adverse effects have been shown to be mediated by oxidative damage to central nervous system. On the other hand, Vit-B12 is known to improve cognitive performance by suppression of oxidative parameters. Thus, in the present study we aimed to test whether treatment by Vit-B12 could prevent ethanol-induced complications in mice using behavioral and biochemical methods. Different groups of male Syrian mice received ethanol, ethanol+Vit-B12, Vit-B12 alone, or saline during adolescence and then learning and memory functions were assessed by Morris water maze (MWM) and Passive Avoidance (PA) tests. Finally, mice were sacrificed for measurement of biochemical factors. Results indicated that, adolescent ethanol intake impairs learning and memory function through exacerbation of oxidative stress and Vit-B12 treatment improves these complications by re-establishment of oxidant/anti-oxidant balance in CNS. Moreover, we found that Vit-B12 prevents ethanol-induced reduction of BDNF and enhancement of GFAP and acetylcholinesterase (AChE) activity. In conclusion, it seems that Vit-B12 supplementation could be used as an effective therapeutic strategy to prevent learning and memory defects induced by chronic alcohol intake during adolescence.

Reinforcement History Dependent Effects of Low Dose Ethanol on Reward Motivation in Male and Female Mice

Alcohol use disorders (AUDs) are more prevalent in men than in women, though AUD diagnoses in women are growing rapidly, making an understanding of sex differences in alcohol-related behaviors increasingly important. The development of AUDs involves the transition from casual, low levels of alcohol drinking to higher, maladaptive levels. The ability of low dose alcohol to drive reward and drug seeking may differ in males and females, and this could underlie differences in susceptibility to AUD. In this study we sought to determine whether a history of chronic, low dose ethanol exposure (0.5 g/kg; i.p.) could drive sucrose reward seeking and motivation, and whether this differed between male and female mice. Adult mice were trained to lever press for a liquid sucrose reward on two reinforcement schedules: a random interval (RI) schedule and a variable ratio (VR) schedule. After training, mice were tested on each of these levers for reward motivation using a progressive ratio test. We found that a history of low dose ethanol exposure increased sucrose reward motivation in male mice, but only on the RI lever and only when exposure occurred proximal to learning. Female mice were more motivated for sucrose on the RI lever than the VR lever regardless of ethanol exposure condition. These findings indicate that training on different reinforcement schedules affects reward motivation. Further, we show that males are more susceptible to the effects of low dose ethanol on sucrose reward motivation than females. These data broaden our understanding of sex differences in reward seeking as a result of ethanol exposure.

Effect of Alcohol on Hippocampal-Dependent Plasticity and Behavior: Role of Glutamatergic Synaptic Transmission

Problematic alcohol drinking and alcohol dependence are an increasing health problem worldwide. Alcohol abuse is responsible for approximately 5% of the total deaths in the world, but addictive consumption of it has a substantial impact on neurological and memory disabilities throughout the population. One of the better-studied brain areas involved in cognitive functions is the hippocampus, which is also an essential brain region targeted by ethanol. Accumulated evidence in several rodent models has shown that ethanol treatment produces cognitive impairment in hippocampal-dependent tasks. These adverse effects may be related to the fact that ethanol impairs the cellular and synaptic plasticity mechanisms, including adverse changes in neuronal morphology, spine architecture, neuronal communication, and finally an increase in neuronal death. There is evidence that the damage that occurs in the different brain structures is varied according to the stage of development during which the subjects are exposed to ethanol, and even much earlier exposure to it would cause damage in the adult stage. Studies on the cellular and cognitive deficiencies produced by alcohol in the brain are needed in order to search for new strategies to reduce alcohol neuronal toxicity and to understand its consequences on memory and cognitive performance with emphasis on the crucial stages of development, including prenatal events to adulthood.

Barriers to developing a valid rodent model of Alzheimer's disease: from behavioral analysis to etiological mechanisms

Sporadic Alzheimer's disease (AD) is the most prevalent form of age-related dementia. As such, great effort has been put forth to investigate the etiology, progression, and underlying mechanisms of the disease. Countless studies have been conducted, however, the details of this disease remain largely unknown. Rodent models provide opportunities to investigate certain aspects of AD that cannot be studied in humans. These animal models vary from study to study and have provided some insight, but no real advancements in the prevention or treatment of the disease. In this Hypothesis and Theory paper, we discuss what we perceive as barriers to impactful discovery in rodent AD research and we offer potential solutions for moving forward. Although no single model of AD is capable of providing the solution to the growing epidemic of the disease, we encourage a comprehensive approach that acknowledges the complex etiology of AD with the goal of enhancing the bidirectional translatability from bench to bedside and vice versa.

Dendritic spine pathology: cause or consequence of neurological disorders?

Altered dendritic spines are characteristic of traumatized or diseased brain. Two general categories of spine pathology can be distinguished: pathologies of distribution and pathologies of ultrastructure. Pathologies of spine distribution affect many spines along the dendrites of a neuron and include altered spine numbers, distorted spine shapes, and abnormal loci of spine origin on the neuron. Pathologies of spine ultrastructure involve distortion of subcellular organelles within dendritic spines. Spine distributions are altered on mature neurons following traumatic lesions, and in progressive neurodegeneration involving substantial neuronal loss such as in Alzheimer's disease and in Creutzfeldt-Jakob disease. Similarly, spine distributions are altered in the developing brain following malnutrition, alcohol or toxin exposure, infection, and in a large number of genetic disorders that result in mental retardation, such as Down's and fragile-X syndromes. An important question is whether altered dendritic spines are the intrinsic cause of the accompanying neurological disturbances. The data suggest that many categories of spine pathology may result not from intrinsic pathologies of the spiny neurons, but from a compensatory response of these neurons to the loss of excitatory input to dendritic spines. More detailed studies are needed to determine the cause of spine pathology in most disorders and relationship between spine pathology and cognitive deficits.

GM1 and piracetam do not revert the alcohol-induced depletion of cholinergic fibers in the hippocampal formation of the rat

Chronic alcohol consumption causes a depletion of the cholinergic fiber network in the rat hippocampal formation, which is not ameliorated by alcohol withdrawal. Following withdrawal from alcohol, there is a further loss of intrinsic hippocampal cholinergic neurons. In this study, we investigated whether treatment with putative neuroprotective agents during the entire withdrawal period would have beneficial effects upon the hippocampal cholinergic innervation. Adult male rats were alcohol-fed for 6 months and subsequently withdrawn from alcohol for 6 months. Some animals were treated with either ganglioside GM1 (35 mg/kg body weight s.c.), vehicle (saline s.c.), or piracetam (800 mg/kg body weight p.o.) for the entire withdrawal period. Choline acetyltransferase (ChAT) immunoreactive (IR) fibers and neurons were analyzed quantitatively in all four animal groups. There were no significant differences in the density of the ChAT-IR hippocampal fiber network when the pure withdrawal and withdrawal + vehicle groups were compared to the withdrawal + GM1 or withdrawal + piracetam groups. In contrast, the number of ChAT-IR interneurons in the hippocampal formation was higher in the withdrawal + GM1 or withdrawal + piracetam groups than in the pure withdrawal and withdrawal + vehicle groups. These results indicate that, in the doses used, neither neuroprotective agent had an effect upon the extrinsic cholinergic innervation, but they had a beneficial effect upon the hippocampal intrinsic cholinergic system.

Abstinent chronic crack-cocaine and crackcocaine/alcohol abusers evidence normal hippocampal volumes on MRI despite persistent cognitive impairments

We measured hippocampal volumes and cognitive functioning in crack-cocaine and crack-cocaine/alcoholdependent subjects (abstinent approximately 10-12 weeks) compared to age-matched controls. Cognitive function was evaluated using the computerized MicroCog Assessment of Cognitive Functioning (which includes tests of explicit, declarative memory subserved by the hippocampus). The hippocampal volumes were quantified on T1-weighted MRIs and were expressed as a proportion of intracranial vault volume. Both subjects and controls showed the larger right versus left hippocampal volume expected in normal anatomy, but we found no differences in hippocampal volume between any of the groups. However, both abstinent cocaine-dependent subjects and abstinent cocaine/alcohol-dependent subjects showed persistent cognitive impairments, including deficits in explicit memory. Our results suggest that either: (1) the hippocampus is resistant to structural volume loss in young and middle-aged cocaine or cocaine/alcohol-dependent subjects, (2) the hippocampal volume loss suffered by young and middle-aged cocaine or cocaine/alcohol-dependent subjects resolves after approximately 3 months of abstinence, or (3) hippocampal atrophy is obscured by the process of gliosis. Further, the cognitive impairments persisting in these abstinent cocaine and cocaine/alcohol-dependent samples may (1) be unrelated to hippocampal function or (2) be associated with abnormal hippocampal function that is not reflected in MRI measures of overall hippocampal atrophy.

The reaction of astrocytes and neurons in the hippocampus of adult rats during chronic ethanol treatment and correlations to behavioral impairments

Chronic ethanol treatment of Wistar rats to 10% (v/v) ethanol over a period of 4, 12, and 36 weeks produced distinct alterations of the glial fibrillary acidic protein immunoreactivity (GFAP-IR) of dorsal hippocampal astrocytes. Ethanol consumption over a period of 4 weeks caused an increase in the total GFAP-IR of the astrocytes. Down-regulation of the total GFAP-IR was measured in all examined brain regions after 36 weeks of ethanol treatment. Prolonged ethanol treatment induced a significant loss of the total number of hippocampal pyramidal and dentate gyrus granule cells. Regional differences in the vulnerability to the neurotoxic effects of chronic ethanol intake over 36 weeks were found: CA3 > CA1 + CA2 > > CA4 > GD. In agreement with the degree of neuronal cell loss, ethanol-induced behavioral impairments were found. The acquisition of maze performance using a complex elevated labyrinth was deteriorated after 36 weeks of ethanol treatment, suggesting a deficit in learning and memory. These findings illustrate the importance of time-response analysis when determining the structural and functional changes produced by chronic ethanol treatment.

Can megadoses of thiamine prevent ethanol-induced damages of rat hippocampal CA1 pyramidal neurones?

The specific aim of this study was to evaluate whether high doses of thiamine can compensate or prevent alcohol-induced damages of rat hippocampus CA1 pyramids. Twenty weeks of ethanol consumption together with a dose of thiamine in the range of 1.19 mg/100 mg food induced significant enlargement (parameters measured were length of the whole spine and diameter of the end-bulb) of dendritic spines. Hypertrophy can be interpreted as a compensation process due to alcohol-induced cell death because viable spines are in search of new synaptic contacts. In contrast, dendritic spines of the alcohol group fed at the same time with a high dose of thiamine (119 mg/ 100 g food = megavitamintherapy) showed normal data concerning these parameters. From these results it may be concluded that a megavitamin therapy supports a neuron's carbohydrate metabolism and therefore could be able to prevent or reduce alcohol-induced damages of hippocampal CA1 pyramidal cells in rat central nervous system.

Metabolic mapping of the effects of chronic voluntary ethanol consumption in rats

The 2-[14C]deoxyglucose method was used to examine the effects of chronic, voluntary ethanol consumption on rates of local cerebral glucose utilization (LCGU). LCGU was measured in male Long-Evans rats immediately following the completion of a 60-min schedule-induced polydipsia drinking session. Three groups of animals were examined: animals with a history of ethanol consumption that received ethanol on the test day (ethanol-ethanol), animals with a similar ethanol history that were presented with water on the test day (ethanol-water), and a control group that received water throughout the experiment (water-water). Ethanol consumption on the test day resulted in a highly discrete pattern of metabolic changes, with significant decreases in glucose utilization in the hippocampal complex, habenula, anterior ventral thalamus, and mammillary bodies, whereas increases were observed in the nucleus accumbens and locus coeruleus. Rates of LCGU in the ethanol-water group were increased throughout all regions of the central nervous system examined, indicating that the long-term consumption of moderate ethanol doses that do not produce physical dependence can cause significant changes in functional brain activity.

Piracetam promotes mossy fiber synaptic reorganization in rats withdrawn from alcohol

Prolonged alcohol intake affects the morphology of the hippocampal formation of the rat and the resulting alterations do not reverse after withdrawal. Actually, an increase of the degenerative activity might occur in this condition. This unexpected observation prompted us to test the efficacy of neuronoprotective drugs during withdrawal. Because in a previous study we found that piracetam, a cyclic derivative of GABA, once added during withdrawal impedes hippocampal cell loss, we decided to evaluate the effect of this compound at the synaptic level. Using unbiased stereological techniques, we estimated the total number of contacts between mossy fibers and CA3 pyramids, as well as the volume and the surface area of the respective pre- and postsynaptic compartments. We found that in piracetam-treated withdrawn rats the number of synapses was higher than that observed in nonpiracetam-treated and alcohol-fed animals. The mechanisms leading to the synaptic reorganization took place at the mossy fiber level. The postsynaptic compartment does not seem to participate in the reorganization. It is suggested that the role of piracetam in this process might depend on the protective effect that this compound has upon glutamatergic receptors.

Chronic ethanol administration decreases brain-derived neurotrophic factor gene expression in the rat hippocampus

We have previously demonstrated that chronic ethanol consumption decreases neurotrophic activity in hippocampal extracts, as assessed by a chick dorsal root ganglia bioassay, but has no effect on hippocampal NGF mRNA or NGF protein levels. We presently report that hippocampal mRNAs encoding neurotrophin-3 and basic fibroblast growth factor are also unaffected. However, in contrast, brain-derived neurotrophic factor mRNA is reliably decreased, thereby suggesting that ethanol-induced damage of the septohippocampal system may at least partially result from an ethanol-induced decrease in hippocampal brain-derived neurotrophic factor expression.

Piracetam impedes hippocampal neuronal loss during withdrawal after chronic alcohol intake

In previous studies we have demonstrated that prolonged ethanol consumption induced hippocampal neuronal loss. In addition, we have shown that withdrawal after chronic alcohol intake augmented such degenerative activity leading to increased neuronal death in all subregions of the hippocampal formation but in the CA3 field. In an attempt to reverse this situation, we tested, during the withdrawal period, the effects of piracetam (2-oxo-1-pyrrolidine acetamide), a cyclic derivative of gamma-aminobutyric acid, as there is previous evidence that it might act as a neuronoprotective agent. The total number of dentate granule, hilar, and CA3 and CA1 pyramidal cells of the hippocampal formation were estimated using unbiased stereological methods. We found out that in animals treated with piracetam the numbers of dentate granule, hilar, and CA1 pyramidal cells were significantly higher than in pure withdrawn animals, and did not differ from those of alcohol-treated rats that did not undergo withdrawal. These data suggest that piracetam treatment impedes, during withdrawal, the pursuing of neuronal degeneration.

Effects of chronic alcohol consumption on the cholinergic innervation of the rat hippocampal formation as revealed by choline acetyltransferase immunocytochemistry

The specific aim of this study was to evaluate whether the cholingeric innervation of the hippocampal formation is affected by chronic alcohol consumption in the rat. Choline acetyltransferase-immunoreactive fibres and neurons were analysed in both alcohol-fed and control rats using a monoclonal antibody against choline acetyltransferase and quantitative methods. We found a global reduction in the cholinergic plexus, which was more pronounced in the hippocampus proper than in the dentate gyrus. The areal density of choline acetyltransferase immunoreactive neurons was also reduced. Differences from controls in neuronal number were particularly striking in the stratum lacunosum moleculare of the regio superior, which is precisely the zone of the hippocampal formation where choline acetyltransferase immunoreactive neurons are more abundant in controls. In conclusion, our results show that prolonged ethanol consumption leads to a substantial reduction in the cholinergic innervation of the hippocampal formation, as there was a loss of cholinergic fibres and also an apparent loss of hippocampal cholingeric neurons. These findings may help to explain the cognitive dysfunctions observed after chronic alcohol consumption.

Stability of [3H]MK-801 binding sites following chronic ethanol consumption

Previous work has demonstrated that short periods (1-2 weeks) of exposure to ethanol produce an upregulation of the N-methyl-D-aspartate (NMDA) receptor complex in hippocampus; an alteration that appears to be associated with the development of physical dependence, because a return to control levels occurs over a 24- to 48-hr abstinence period. Prolonged periods of chronic ethanol treatment (CET; 4-8 months of treatment) have been shown to produce severe and permanent alterations in the morphological and functional characteristics of hippocampal pyramidal neurons. Several lines of research have demonstrated that the NMDA receptor complex is involved in excitotoxic cell loss during certain pathological states. On the basis of this evidence, we hypothesized that prolonged ethanol exposure would be accompanied by an enduring increase in NMDA receptors and that NMDA receptor binding in cells surviving CET would be altered. To test this hypothesis, we measured the binding characteristics of the NMDA receptor complex in a variety of brain structures following CET. Animals were fed a nutritionally complete, ethanol-containing diet for 28 weeks and then allowed a 48-hr abstinence period. A control group was fed the same diet, except sucrose was isocalorically substituted for ethanol. We first examined the effect of CET on the binding properties of a noncompetitive antagonist to the NMDA receptor channel, [3H]diclozipene ([3H]MK-801). Next, as an indirect examination of NMDA receptor function, we measured the ability of glutamate to stimulate channel opening and thus [3H]MK-801 binding. In all brain structures examined, neither the Kd nor the Bmax of [3H]MK-801 binding to the NMDA receptor was altered following CET. In addition, no effect of treatment was seen on the ability of glutamate to stimulate [3H]MK-801 binding.

Zinc deficiency and corticosteroids in the pathogenesis of alcoholic brain dysfunction--a review

Chronic alcoholism is associated with hypercortisolemia and low serum zinc (Zn). Hypercortisolemia could be responsible for alcoholic cerebral atrophy and is also associated with enhanced NMDA neurotoxicity. It is hypothesized that low brain Zn, noted in chronic alcoholics, enhances NMDA excitotoxicity and ethanol withdrawal seizure susceptibility. Also, Zn deficiency can produce neuronal damage through increased free radical formation. Clinically, Zn replacement therapy may be a rational approach to the treatment of alcohol withdrawal seizures and alcohol-related brain dysfunction.

Effects of chronic alcohol consumption and withdrawal on the somatostatin-immunoreactive neurons of the rat hippocampal dentate hilus

Previous studies have demonstrated that the dentate granule and the CA3 pyramidal cells of the rat hippocampal formation are neuronal populations vulnerable to the toxic effects of ethanol. It also has been shown that the resulting alterations do not end after withdrawal from ethanol. As the neurons in the dentate hilus are heavily interconnected with the dentate granule cells, the authors decided to examine the fate of the hilar neurons after chronic alcohol consumption and withdrawal, inasmuch as the hilar somatostatin-immunoreactive (SS-I) neurons were found to be sensitive to cerebral ischemia and to seizures. The following groups of adult rats were studied: (1) alcohol-fed for 6 and 12 months; (2) alcohol-fed for 6 months and then switched to water for a further 6 months; (3) pair-fed controls; and (4) controls fed ad libitum. The authors determined the numerical density of hilar neurons and the number of its SS-I subpopulation. These were found to be significantly reduced in both the alcohol-fed and withdrawal groups when compared with the respective age-matched controls. The consequent loss of the integrative action of the hilar neurons, including the SS-Is, could explain some of the alcohol-related functional deficits as well as their persistence after withdrawal.

Effect of chronic ethanol on the septohippocampal system: a role for neurotrophic factors?

The mechanisms by which chronic ethanol exposure produces neuronal damage have not been established. Potentially ethanol may reduce normal neurotrophic influences necessary for neuronal survival, growth, and function. We hypothesized that chronic ethanol exposure might produce a decrease in the synthesis, availability, upregulation, delivery, and/or the biological activity of normally occurring neurotrophic factors, or may alter the capacity of target neurons to respond to these factors. The available evidence leading to this hypothesis and supporting data from our laboratory are discussed.

Structural changes in the hippocampal formation after long-term alcohol consumption and withdrawal in the rat

The effects of long-term alcohol consumption and withdrawal upon the structure of the rat hippocampal formation were studied by applying morphometric methods to material processed for light and electron microscopy. The somatostatinergic neurons of the hilus were also studied. Groups of 6 rats were treated as follows: (a) given alcohol for 6, 12 and 18 months; (b) paired controls; and (c) rats switched to a normal diet in the 6 months after 6 and 12 months of alcohol intake. A progressive loss of hippocampal neurons after chronic alcohol consumption was found. The loss was aggravated during withdrawal from alcohol, with the exception of the hilar cells. The dendrites of granule cells from the alcohol-treated rats displayed signs of regrowing, but they did not do so in rats withdrawn from alcohol. The synapses between mossy fibre terminals and CA3 dendrites appear to be rather resistant to alcohol insult, and evidence of morphological plasticity was found in withdrawn rats. If an homology can be established between humans and rodents then the changes observed in alcohol-fed rats can be regarded as underpinning some of the functional and behavioural alterations depicted under these circumstances. The peculiar changes found in some nerve cell populations after withdrawal of alcohol could be related to the deficient or incomplete functional recovery often seen after abstinence from alcohol.

The effect of chronic ethanol intake on brain NGF level and on NGF-target tissues of adult mice

The effect of ethanol consumption on the forebrain and hypothalamus of adult mice was investigated. A consistent decrease of biological activity and of nerve growth factor (NGF) immunoreactivity was observed in the hippocampus and hypothalamus of alcohol-treated mice. Biochemical studies also indicate that chronic ethanol intake causes a reduction in the level of choline-acetyltransferase in the septum, hippocampus and striatum, but not in the cortex and other brain regions. This study provides evidence that long-term ethanol intake causes impairment of brain NGF level and of the cholinergic enzyme, regulated by NGF, suggesting that NGF synthesis and/or biological activity is affected in alcohol-related brain neuropathology.

Chronic ethanol consumption reduces the neurotrophic activity in rat hippocampus

The effect of chronic ethanol treatment (CET) for 21-26 weeks on the neurotrophic activity contained in the rat hippocampus (HPC) was determined with a bioassay in cultures of dissociated dorsal root ganglion cells (DRG) obtained from E7-8 chick embryos. Extracts of the HPC from CET or pair-fed control rats were used as experimental media, and neuronal survival and neurite-outgrowth of DRG cultures were determined. Both neuronal survival (-25%) and neurite-outgrowth (-50%) were reduced in the presence of HPC extracts from CET rats relative to controls. These data suggest that CET reduces the neurotrophic content of the HPC which may result in damage to septohippocampal neurons.

The effect of long-term alcohol intake on brain NGF-target cells of aged rats

It was reported that chronic exposure to ethanol causes a loss of hippocampal pyramidal cells and of brain cholinergic neurons in both laboratory animals and humans. In the present study, it was hypothesized that nerve growth factor (NGF), a trophic agent for the survival and maintenance of basal forebrain cholinergic neurons (FCN), might be affected by the neurodegenerative events which occur during ethanol consumption. To test this hypothesis, we used aged rats (14 months) exposed for 16 weeks to 40 g/kg per day of undiluted wine. Our experiments showed that chronic alcohol consumption causes a reduction of NGF in the hippocampus (HI) and of choline acetyltransferase (ChAT) activity in both the septum and the HI and a reduction in the distribution of NGF-receptors (NGF-R) in the septum and nucleus of Meynert. Intracerebral injection of NGF in alcohol-exposed rats results in a return to normal levels of ChAT enzymatic activity and NGF-R expression. These experiments indicate that the damaging effect of alcohol on the FCN is also associated with impairment of central NGF-target structures.

Terminal vessels of dentate gyrus in chronically alcohol-intoxicated rats

Quantitative changes in the microvasculature of the central nervous system of the rat following chronic ethanol intoxication were studied. For 6 months, 12 rats drank only 25% ethanol and eight control rats only water. After fixation by perfusion, semithin sections of dentate gyrus were obtained. In each one, semiautomatic measurements were made of the length, surface, and volume densities, and the mean area of a terminal vessel cross-section and the results were evaluated statistically. Chronic ethanol intoxication caused an increase in the length and surface density, a decrease in the mean cross-sectional area, whereas the volume density of terminal vessels was unchanged. These results show that the reduction of the mean surface area of terminal vessels after prolonged ethanol intoxication is compensated by the increase of other morphometrically measurable parameters, i.e., length and surface density. As a consequence of these alterations, the volume density remains unchanged. The results indicate great reactivity of the microvascular system of the dentate gyrus in chronically ethanol-intoxicated rats.

Short-term ethanol intoxication in rat. Effect on the entorhinal cortex

The effect of short-term ethanol intoxication in systems implicated in memory and other cognitive functions in rats has been assessed by studying the variation in the karyometry of the neurons in the different layers of the lateral entorhinal cortex. The analysis showed that short-term ethanol consumption produced a reduction in the nuclear area of neurons in layers V and VI, and to a lesser extent, in layers II and III. These results suggest that the deep layers of the entorhinal cortex are more sensitive to ethanol intoxication, thus more likely affecting cortical and subcortical projections than the hippocampal output.

Effects of long durations of ethanol treatment during aging on dendritic plasticity in Fischer 344 rats

Twelve-month-old Fischer 344 rats were fed a liquid diet containing 35% ethanol until they were 18 or 24 months old. Pair-fed and chow-fed control rats were matched to each ethanol-fed rat for concurrent treatment. Cerebellar Purkinje cell networks were measured in half of the rats at the end of the ethanol treatment and in the remaining rats after a subsequent 2-month recovery period. Chronic ethanol consumption resulted in significant elongation of terminal segments in the networks, and the unpaired terminal segments were the predominant sites of this growth. An increase in the duration of ethanol consumption from 24 to 48 weeks caused significantly greater segment elongation in the ethanol-fed rats in spite of the fact that circulating blood levels of ethanol declined markedly with the increased duration of treatment. During the same period of time, a pattern of terminal segment regression followed by terminal segment regrowth characterized age-induced changes in these networks. Thus the effects of long-term ethanol consumption were distinct from effects of concurrent aging processes in the Purkinje cell networks. There were significant interactions between the diets and the longer duration of treatment, such that as segments elongated in the ethanol-fed rats, they shortened in the pair-fed rats, and between the diets and the recovery period, such that as segments elongated during recovery in the pair-fed rats, they shortened in the ethanol-fed rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of GM1 ganglioside upon neuronal degeneration during withdrawal from alcohol

In previous studies we demonstrated that chronic alcohol consumption induced hippocampal cell and synapse loss in offset with an increase in the length of granule cell dendrites. In addition we observed that withdrawal after long periods of alcohol intake worsened the degenerative processes and that dendritic alterations were no longer apparent. In an attempt to reverse these structural changes we tested the action of GM1 ganglioside during the withdrawal period as there is evidence that GM1 may enhance neuronal recovery after different kinds of brain lesions. Cell and synaptic quantifications were performed and the branching pattern of the granule cell dendritic arborizations was analysed. The number of dentate granule and CA3 pyramidal cells from GM1-treated animals was found not to be significantly different from that of the alcohol-treated and withdrawal groups. No quantitative changes were found in the number of mossy fiber-CA3 pyramidal cell synapses when the aforementioned groups were compared. Whether the lack of effectiveness of GM1 can be related to the model employed or not is thoroughly discussed.

Effects of alcoholization on the rat hippocampus

The effects of ethanol intoxication on the hippocampus (H) has been studied in 18 (5 died) Sprague-Dawley rats (group A), 5 other rats served as control (group C). The weight of the animals at the beginning of experiment was 135-140 g and, at the end, 234 g for group A and 240 g for group C. Both groups were given a liquid diet. In group A, the ethanol provided 36% of the total calories; in group C these calories were supplied as dextrin-maltose. The average of the diet alcoholemia was 159.6 mg/100 ml. After 70 days of alcohol intake, the rats were transcardially perfused, and brain and liver were removed. The liver of the alcoholic rats exhibited an intense steatosis, and the H showed important modifications in number of neurons as well as in nuclear size. The neuron loss in group A, with respect to group C was: highly significant (P less than 0.001) for CA2; very significant (P less than 0.01) for CA3 and CA4; in CA1 and GD the reduction was not significant. In spite of neuron loss, the nuclear area showed a reduction in size: highly significant in CA2 and CA4; very significant in GD, but in CA2 and CA3 the reduction did not reach statistical significance. These results confirm the lethal influence of ethanol on some neurons, and the limited ability of the remnant neurons to compensate for neuronal loss.

Differential effects of chronic ethanol consumptions or thiamine deficiency on spatial working memory in Balb/c mice: a behavioral and neuroanatomical study

This study was aimed to compare the effects of either a thiamine deficiency or a chronic ethanol consumption on memory and on neuronal density within the median mammillary nucleus. Results showed that alcohol-treated (48 weeks) mice exhibited a behavioral impairment in a sequential alternation task characterized by a progressive decay of alternation rates as a function of the number of trials; such a deficit was not observed in controls and thiamine-deficient subjects. A quantitative analysis using histological sections showed an important reduction of neuronal density within the mammillary bodies following the alcohol treatment but not following thiamine deficiency.

The threshold concentration of dietary ethanol necessary to produce toxic effects on hippocampal cells and synapses in the mouse

A nutritionally complete liquid diet containing 0, 3, 5, or 7% ethanol was fed to C57 mice for 4 months and killed after a further 4 months on a standard food pellet diet. The number of pyramidal cells in Araldite sections of the hippocampus was not significantly reduced in any group relative to the zero alcohol intake group. Synaptic counts in the area occupied by the pyramidal cell basal dendrites showed the 7% alcohol group to have a reduced number of synaptic contacts, with no convincing differences between the other groups relative to the zero alcohol group. All measurements made collectively could not be used to distinguish 3 or 5% ethanol consuming animals from 0% ethanol consuming animals. Significant differences in body weight and dry brain weight were detected in the comparison of the group treated with 7% ethanol and 4-month recovery with the group receiving the 0% ethanol dose and 4-month recovery. It is concluded that maintaining mice on a diet containing not more than 5% ethanol has no adverse long-term structural effects on hippocampal pyramidal cells or synapses.

Granule cell loss and dendritic regrowth in the hippocampal dentate gyrus of the rat after chronic alcohol consumption

The effects of chronic alcohol consumption (CAC) on the relative number of dentate gyrus granule cells and their dendritic trees, were studied in animals fed alcohol for 6, 12 and 18 months and in their respective controls. The granule cell density was estimated with the unbiased disector method. Following 6 months of alcohol consumption, the thickness of the dentate gyrus granular layer and the relative number of dentate granule cells were significantly decreased when compared with controls. The granule cell dendritic arborizations showed an increase of their dendritic extent in alcohol-treated rats. No significant differences were found in the density of dendritic spines between alcohol-fed and control animals. These results indicate the existence of hippocampal granule cell dendritic regrowth in alcohol-fed rats, probably occurring as a compensatory response to the granule cell deficit which follows the alcohol-induced granule cell degeneration. These degenerative and regenerative changes might have functional implications for the organization of the synaptic hippocampal circuitry after long periods of alcohol consumption.

Alterations and recovery of dendritic spine density in rat hippocampus following long-term ethanol ingestion

Neuronal loss and dendritic pathology are often observed in humans and animals after long-term ethanol ingestion. It is not known, however, if surviving but damaged neurons can recover normal structure during ethanol abstinence. We quantified dendritic spine density in two neuronal populations in rat hippocampus to investigate whether reversibility from the cellular neurotoxic sequelae of chronic ethanol exposure was possible. Male Long-Evans rats were maintained for 20 weeks on an ethanol-containing liquid diet. Controls were pair-fed a liquid diet with sucrose substituted isocalorically for ethanol. One-half of each group was sacrificed at the end of the 20-week treatment and one-half was given a 20-week ethanol-free recovery period period to sacrifice. Analysis of rapid Golgi material revealed a decreased spine density in CA1 pyramidal cells that increased to control level during abstinence, and an increased spine density in dentate gyrus granule cells that was reduced toward control level during abstinence. Thus, despite the fact that chronic ethanol exposure produced differential initial effects, the return toward normal spine density in each region is consistent with the concept of neuronal recovery and reorganization during abstinence from ethanol.

Long-term alcohol consumption reduces the number of neuronal nuclear pores. A morphometric study undertaken in CA3 hippocampal pyramids of rats

A close relationship between the number of nuclear pores and the cellular protein synthesis activity is known to exist. Previous biochemical investigations lead to admit that the widespread neuronal alcohol-induced degenerative changes could depend on a decrease in the neuronal protein synthesis. The morphometric analysis made on the nuclear pore complexes of CA3 hippocampal pyramids of long-term alcohol-fed rats fully supports this attractive hypothesis, since it has been found a marked reduction in the number of pores per unit surface area of nuclear membrane, together with a reduction in their total number per nucleus.

Repeated withdrawal from ethanol on radial arm acquisition in rats

Male rats were treated with ethanol (8.0-12.0 g/kg/day) for four 2 week periods interrupted every 2 weeks by a 2 week period of no drug treatment. Thus they experienced withdrawal from ethanol four times. Other rats were treated with ethanol for 8 weeks with no interruptions, to control for the total dose and duration of drug treatment. Acquisition of an eight-arm radial maze response when daily ethanol treatment was ended, was not affected by either the experience of four withdrawals from ethanol or by 8 weeks of ethanol treatment. The lack of withdrawal-induced impairment can be attributed to a lack of sensitivity in the maze task to possible withdrawal-induced deficits and to an insufficient duration of ethanol dependence.

Build-up and release from proactive interference during chronic ethanol consumption in mice: a behavioral and neuroanatomical study

Male mice of the BALB/c strain were given a solution of 15% ethanol as their only source of fluid during either 24 or 48 weeks. They were submitted to a sequential alternation (SA) task in a T-maze (6 successive trials). It was found that 48 but not 24 weeks of alcohol administration lead to a deficit as compared to pair-fed or tap-water controls. Whereas experimental mice performed as well as controls on the first 3 choices, they exhibited a gradual decrease in the SA rate on subsequent trials. We suggest that this deficit might result from an exaggerated vulnerability to proactive interference (PI). In order to further test this hypothesis, a second experiment investigated whether a between-trials variation of context of the maze would increase performance. It was found that the SA rate improved as soon as the variation was provided (5th trial). We suggest that the deficit of experimental mice results from an impairment of retrieval processes. A neuroanatomical study was conducted to quantify cell losses resulting from 8, 24 or 48 weeks of ethanol treatment in the mammillary bodies (MM) or the hippocampus (HPC). At the time of appearance of the deficit, MM exhibited a -32% cellular loss, whereas this was only -18% in the HPC. This result emphasises the importance of MM lesion in memory deficits resulting from long-term alcohol consumption.

Effect of chronic ethanol consumption on the fine structure of the dentate gyrus in long-sleep and short-sleep mice

The effect of short- and long-term chronic ethanol consumption on the fine structure of the dentate gyrus was examined in two lines of mice selected for their differential sensitivity to acute ethanol administration. Quantitative electron microscopic analysis of dendritic spines, axon terminals, and synaptic appositions revealed significant differences between the long-sleep and short-sleep mice. In control preparations, long-sleep mice were found to have larger spine areas and perimeters, larger axon terminals, and longer synaptic appositions than short-sleep mice. In addition, the shape of dendritic spines in the long-sleep mice was significantly more complex than those of short-sleep mice. Ethanol tended to increase this complexity in long-sleep mice only. Ethanol had only a limited effect on the other anatomical measures. The results provide evidence for ultrastructural differences between the nervous systems of these lines of mice which may have a role in their differential sensitivity to acute ethanol administration.

Neuroanatomical effects of chronic ethanol consumption on dorsomedial and anterior thalamic nuclei and on substantia innominata in mice

Quantitative analysis, using histological sections, showed that chronic ethanol consumption for 7 months produced a weak but significant cellular loss in the dorsomedial thalamic nucleus, anterior thalamus and substantia innominata in the mouse. These results are in agreement with patterns of neuroanatomical damage observed in human alcoholics.

Effects of long-term ethanol consumption on GABAergic neurons in the mouse hippocampus: a quantitative immunocytochemical study

The effects of 6 months' ethanol consumption by mice on hippocampal GABAergic neurons were investigated by means of an immunocytochemical method using GABA antibodies. Although ethanol treatment did not modify body or brain weights in our experimental conditions, two differences were observed in ethanol-treated mice, as compared to controls: a decrease in the labelling intensity of immunopositive neurons and fibers in the dorsal and the ventral parts of the hippocampus; and a decrease in the number of immunopositive neurons. This neuronal loss was statistically significant in the ventral hippocampus only, where it reached about 25% in the stratum radiatum. It is concluded that chronic ethanol consumption leads to a decrease in GABA content of hippocampal neurons and to a loss of GABAergic neurons, mostly in the ventral part of the hippocampus. These alterations in GABAergic transmission could be related to the well known functional deficits observed in chronic alcoholism.

Effects of chronic ethanol treatment on neocortex

Neocortical inhibition and neuronal morphology were studied in rats following chronic ethanol treatment (CET). In terminal acute experiments, spontaneous neuronal discharges in pair-fed and naive rats were inhibited by epicortical stimulation, a procedure known to produce postsynaptic inhibition. Few units in CET rats were inhibited by such stimulation. Cortical recurrent inhibition, indicated by a surface-negative potential in response to antidromic stimulation of the cerebral peduncle, was little affected by a challenge dose of ethanol, compared with the response in pair-fed animals. Recurrent inhibition involves inhibitory interneurons. CET apparently made inhibitory interneurons and inhibitory postsynaptic receptors less responsive to ethanol. Apical dendritic spines on some portions of pyramidal neurons increased in number with CET. This could reflect a compensatory growth in neurons not damaged by CET. The overall observations are consistent with ethanol affecting one or more specific systems of cortical motor control as opposed to its presumed general disinhibitory effect.

Chronic ethanol consumption induces neuronal loss in mammillary bodies of the mouse: a quantitative analysis

Quantitative analysis, using histological sections, showed that chronic ethanol consumption in the mouse produced neuronal loss in the medial mammillary bodies. This cellular loss was not uniform and was more marked in posterior (-30.1%) than in anterior (-8.8%) parts. Moreover, a reduction of the nucleus diameter of the remaining neurons was found. These results are in agreement with patterns of neuroanatomical damage observed in human alcoholics.