Alcohol and central neurotransmission

The Dopamine System in Mediating Alcohol Effects in Humans

Brain-imaging studies show that the development and maintenance of alcohol use disorder (AUD) is determined by a complex interaction of different neurotransmitter systems and multiple psychological factors. In this context, the dopaminergic reinforcement system appears to be of fundamental importance. We focus on the excitatory and depressant effects of acute versus chronic alcohol intake and its impact on dopaminergic neurotransmission. Furthermore, we describe alterations in dopaminergic neurotransmission as associated with symptoms of alcohol dependence. We specifically focus on neuroadaptations to chronic alcohol consumption and their effect on central processing of alcohol-associated and reward-related stimuli. Altered reward processing, complex conditioning processes, impaired reinforcement learning, and increased salience attribution to alcohol-associated stimuli enable alcohol cues to drive alcohol seeking and consumption. Finally, we will discuss how the neurobiological and neurochemical mechanisms of alcohol-associated alterations in reward processing and learning can interact with stress, cognition, and emotion processing.

Pre-clinical models of reward deficiency syndrome: A behavioral octopus

Individuals with mood disorders or with addiction, impulsivity and some personality disorders can share in common a dysfunction in how the brain perceives reward, where processing of natural endorphins or the response to exogenous dopamine stimulants is impaired. Reward Deficiency Syndrome (RDS) is a polygenic trait with implications that suggest cross-talk between different neurological systems that include the known reward pathway, neuroendocrine systems, and motivational systems. In this review we evaluate well-characterized animal models for their construct validity and as potential models for RDS. Animal models used to study substance use disorder, major depressive disorder (MDD), early life stress, immune dysregulation, attention deficit hyperactivity disorder (ADHD), post traumatic stress disorder (PTSD), compulsive gambling and compulsive eating disorders are discussed. These disorders recruit underlying reward deficiency mechanisms in multiple brain centers. Because of the widespread and remarkable array of associated/overlapping behavioral manifestations with a common root of hypodopaminergia, the basic endophenotype recognized as RDS is indeed likened to a behavioral octopus. We conclude this review with a look ahead on how these models can be used to investigate potential therapeutics that target the underlying common deficiency.

Effect of voluntary alcohol consumption on Maoa expression in the mesocorticolimbic brain of adult male rats previously exposed to prolonged maternal separation

Discordant associations between monoamine oxidase A (MAOA) genotype and high alcohol drinking have been reported in human and non-human primates. Environmental influences likely moderate genetic susceptibility. The biological basis for this interplay remains elusive, and inconsistencies call for translational studies in which conditions can be controlled and brain tissue is accessible. The present study investigated whether early life stress and subsequent adult episodic alcohol consumption affect Maoa expression in stress- and reward-related brain regions in the rat. Outbred Wistar rats were exposed to rearing conditions associated with stress (prolonged maternal separation) or no stress during early life, and given free choice between alcohol and/or water in adulthood. Transcript levels of Maoa were assessed in the ventral tegmental area, nucleus accumbens (NAc), medial prefrontal cortex, cingulate cortex, amygdala and dorsal striatum (DS). Blood was collected to assess corticosterone levels. After alcohol consumption, lower blood corticosterone and Maoa expression in the NAc and DS were found in rats exposed to early life stress compared with control rats. An interaction between early life stress and voluntary alcohol intake was found in the NAc. Alcohol intake before death correlated negatively with Maoa expression in DS in high alcohol-drinking rats exposed to early life stress. Maoa expression is sensitive to adulthood voluntary alcohol consumption in the presence of early life stress in outbred rats. These findings add knowledge of the molecular basis of the previously reported associations between early life stress, MAOA and susceptibility to alcohol misuse.

The Loudness Dependence of Auditory Evoked Potentials (LDAEP) in individuals at risk for developing bipolar disorders and schizophrenia

OBJECTIVES

The Loudness Dependence of Auditory Evoked Potentials (LDAEP) is considered as an indicator of central serotonergic activity. Alteration of serotonergic neurotransmission was reported in bipolar disorders and schizophrenia. In line with previous reports on clinically manifest disorders, we expected a weaker LDAEP in subjects at risk for bipolar disorders and schizophrenia compared to healthy controls.

METHODS

We analyzed LDAEP of individuals at risk for developing bipolar disorders (n=27), with high-risk status (n=74) and ultra-high-risk status for schizophrenia (n=86) and healthy controls (n=47).

RESULTS

The LDAEP did not differ between subjects at risk for schizophrenia or bipolar disorders and controls. Among subjects without medication (n=122), the at-risk-bipolar group showed a trend towards a weaker LDAEP than both the high-risk and the ultra-high-risk groups for schizophrenia.

CONCLUSIONS

The LDAEP did not appear as a vulnerability marker for schizophrenia or bipolar disorders. This suggests that an altered LDAEP may not be measurable until the onset of clinically manifest disorder. However, the hypothesis that pathogenic mechanisms leading to bipolar disorders may differ from those leading to schizophrenia is supported.

SIGNIFICANCE

This is the first study investigating LDAEP in a population at risk for bipolar disorders.

Alcohol administration during adulthood induces alterations of parvalbumin and glial fibrillary acidic protein immunoreactivity in rat hippocampus and cingulate cortex

Alcohol induces impairment of cognition, learning and memory. Neurotoxic effects of alcohol on the pathology of the hippocampus and the cingulate cortex were investigated in experimental rats. Parvalbumin (PV), a calcium-binding protein, is a crucial component of GABAergic neurons and glial fibrillary acidic protein immunoreactive (GFAP-ir) astrocytes have been used as markers. We investigated the effects of ethanol exposure during adulthood on the PV-ir neurons and GFAP-ir astrocytes in the hippocampus and the cingulate cortex of 3-month-old male Wistar rats. The rats were divided into 2 groups: control (C) and alcohol-exposed groups. The control group received distilled water whereas the alcohol-exposed groups received either a low dose (20%w/v, LD) or high dose (40%w/v, HD) of ethanol for periods of 21 days, 3 or 6 months. The brains of the animals were processed for immunohistochemistry using anti-parvalbumin and anti-GFAP antibodies and the numbers of PV immunoreactive (PV-ir) neurons and GFAP-ir astrocytes were counted/unit area. For each period of administration, the number of PV-ir neurons was significantly reduced for groups exposed to both the low and the high doses of ethanol compared to those of control groups in both the hippocampus and the cingulate cortex (p<0.01). In addition, the number of PV-ir neurons was progressively reduced after prolonged ethanol exposure. In contrast, there was a significantly increased number of GFAP-ir astrocytes observed in the hippocampus and the cingulate cortex in all groups exposed to ethanol and this was a function of both the duration and the dose of ethanol exposure, indicating that PV-ir neurons are as sensitive as the GFAP-ir astrocytes to ethanol exposure. Our data indicate that alcohol exposure induced a reduction of PV-ir neurons and an increase of GFAP-ir astrocytes in the hippocampus and the cingulate cortex and this may be associated with the impairment of cognition, learning and memory after chronic alcohol administration.

Chronic progesterone treatment augments while dehydroepiandrosterone sulphate prevents tolerance to ethanol anxiolysis and withdrawal anxiety in rats

We have recently shown that the neurosteroid allopregnanolone modulates anxiolytic effect of ethanol. In the present report, we attempted to examine whether neurosteroids progesterone and dehydroepiandrosterone sulphate (DHEAS), which modulate gamma-aminobutyric acid (GABA(A)) receptor function, affects development of tolerance to ethanol anxiolysis and withdrawal anxiety. Rats on ethanol (6% v/v in nutritionally balanced liquid diet) for prolong period (10 days) were injected twice daily either with vehicle, progesterone (a precursor of allopregnanolone, positive GABA(A) receptor modulator), finasteride (5alpha-reductase inhibitor) or DHEAS (negative GABA(A) receptor modulator). During this period, rats were acutely challenged periodically with ethanol (2 g/kg, i.p., 8% w/v) and subjected to the elevated plus maze test. For withdrawal studies, similar treatment protocols (except ethanol challenge) were employed and on day 11, rats were subjected to the elevated plus maze test at different time intervals post-ethanol withdrawal. While progesterone significantly advanced the development of tolerance to ethanol anxiolysis and enhanced withdrawal anxiety, DHEAS and finasteride prevented such behavioral alterations. These data highlight the important role played by GABAergic neurosteroids progesterone and DHEAS in the development of tolerance to ethanol anxiolysis and withdrawal anxiety in rats. Moreover, it points to the potential usefulness of specific neurosteroids as targets in the treatment of alcoholism.

Effects of chronic ethanol administration on the expression levels of neurotrophic factors in the rat hippocampus

Chronic ethanol consumption has adverse effects on the central nervous system. Hippocampus is one of the target sites of ethanol neurotoxicity. Hippocampal damage is known to result in impairment of learning and memory. This study was aimed to determine whether chronic ethanol consumption could alter the expression levels of brain-derived neurotrophic factor (BDNF) and glial-derived neurotrophic factor (GDNF) mRNAs in the hippocampus. Male Wistar rats were given unrestricted access to a liquid diet containing 5% (v/v) ethanol as the sole fluid source for 19 weeks beginning at 10 weeks of age. The expression levels of BDNF and GDNF mRNAs in the hippocampus were analyzed by real-time reverse transcription-polymerase chain reaction (RT-PCR) analysis. The present study revealed that chronic ethanol consumption did not result in significant changes in the expression levels of BDNF and GDNF mRNAs. Our present results showed no significant alteration in the expression of these neurotrophic factors; these results will lead to further studies to examine the possible alterations in the gene expression of various neurotrophins that are related to hippocampal functions including learning and memory.

Alcohol consumption alters dopamine transporter sites in Wistar–Kyoto rat brain

Even though animal and human studies show alterations in dopamine transporter (DAT) sites after alcohol withdrawal, the role of DAT in influencing either alcoholic or depressive behavior has not been examined extensively. Given that the Wistar-Kyoto (WKY) rat is a putative animal model of depressive behavior, the present study examined the effects of chronic alcohol consumption on DAT sites in WKY versus Wistar (WIS) rats. Brains from both strains were sectioned for autoradiographic analysis of [3H]-GBR12935 binding to DAT sites after 24 days of alcohol exposure. The results indicated that WKY rats consumed a greater amount of alcohol (P < 0.001) than WIS rats did throughout the experiment. Autoradiographic analyses of discrete brain regions indicated that alcohol consumption increased DAT sites in a greater number of brain areas in WKY compared to WIS rats. In WKY rats, the binding of [3H]-GBR12935 to DAT sites was increased in the basolateral, central and lateral nuclei of the amygdala, lateral nucleus of the hypothalamus, olfactory tubercle, caudate-putamen, nucleus accumbens and substantia nigra (P < 0.05) and decreased in the ventromedial nucleus of the hypothalamus and the CA1 region of the hippocampus. In WIS rats, alcohol consumption increased DAT sites in the CA1 region of the hippocampus, basolateral nucleus of the amygdala, ventral tegmental area and substantia nigra, and decreased DAT sites in the lateral and ventromedial hypothalamus and dentate gyrus. These results indicate a strain dependent alteration in DAT sites which may be related to altered dopamine neurotransmission in select brain regions following alcohol consumption.

Magnesium Treatment of Primary Alcohol-Dependent Patients During Subacute Withdrawal: An Open Pilot Study With Polysomnography

BACKGROUND

Sleep electroencephalogram alterations and insomnia complaints persist after alcohol withdrawal in dependent patients and are considered strong predictors of relapse. Although disturbances of magnesium household due to alcohol consumption are well known, the relationship of magnesium metabolism and sleep disturbances has not been investigated in this patient group. We conducted an open pilot study to evaluate the effects of magnesium treatment on the sleep of primary alcohol-dependent patients during subacute withdrawal.

METHODS

Patients were treated with 30 mmol magnesium daily over 4 weeks. Eleven of the 14 included patients were evaluated. Patients were free of any kind of psychotropic medication or other substances known to influence sleep. Polysomnographic recordings with monitoring of periodic leg movements in sleep (PLMS) were performed for two consecutive nights 2 weeks after acute withdrawal (baseline) and 4 weeks later at the end of the treatment period. After the baseline polysomnography, patients were investigated by the magnesium loading test to verify magnesium depletion.

RESULTS

We found a significant decrease of sleep onset latency from 40.6 to 21.7 min (p = 0.03) and a significant improvement of subjective sleep quality, as assessed by the Pittsburgh Sleep Quality Index, from 8.1 to 5.8 (p = 0.05) during magnesium treatment. Changes in PLMS indices revealed two subgroups of patients: one with an increase of PLMS from 30.7 to 39.4 per hour of sleep (n = 4) and the other one with a decrease of PLMS from 8.9 to 2.1 per hour of sleep (p = 0.04). Patients with PLMS decreases seemed to have a more favorable prognosis: total sleep time, gamma-glutamyltransferase, carbohydrate-deficient transferrin, and Beck Depression Inventory scores improved significantly during treatment in this group. The magnesium loading test revealed a magnesium deficiency in only one patient, five patients showed normal retention values, and the remaining five patients had an increased magnesium excretion, indicating a possible continued renal magnesium loss during abstinence.

CONCLUSIONS

The results of this study should be interpreted with caution, because no control group with placebo was investigated. Both subjective and, partly, objective parameters of sleep improved during the 4-week study period. Further research is needed to clarify the relationship of magnesium metabolism and sleep alterations.

Imbalance between neuroexcitatory and neuroinhibitory amino acids causes craving for ethanol

Long-term exposure to ethanol leads to an imbalance in different excitatory and inhibitory amino acids. When ethanol consumption is reduced or completely stopped, these imbalances in different amino acids and neurotransmitters are behaviorally expressed in the form of ethanol withdrawal. Glutamate, a major excitatory amino acid, and GABA, a major inhibitory amino acid, are responsible, at least partly, for ethanol withdrawal symptoms. The hypofunction of GABAA receptors and enhanced function of NMDA receptors are suggested to be responsible for the increase in the behavioral susceptibility during ethanol withdrawal. This imbalance between receptors may be exacerbated by repeated withdrawal. Because multiple and repeated periods of chronic ethanol consumption and withdrawal often occur in alcohol abusers, animal studies on the neurochemical changes in different amino acids following chronic ethanol treatment (CET) that is interrupted by repeated ethanol withdrawal episodes may be of clinical relevance for the development of treatment strategies. Brain glutamate increases during the first cycle of ethanol withdrawal, and this increase is much higher during the third cycle of ethanol withdrawal. The elevated glutamate released in the hippocampus during the first cycle of ethanol withdrawal episode was exacerbated in subsequent withdrawal episodes. Acamprosate, a drug used during human alcohol detoxification, is able to completely block the glutamate increase observed during the first as well as the third withdrawal of ethanol. In ethanol-naïve rats, there was no change in the glutamate microdialysate content after an acute ethanol injection. However, when repeated ethanol injections were cued with a vinegar stimulus that had previously been associated with the same ethanol injection, a significant increase in glutamate microdialysate content was assayed. Furthermore, when the cue was omitted, the ethanol injection induced no changes in glutamate microdialysate content in rats that had been previously ethanol conditioned. By comparison, a saline injection had no effect on extracellular glutamate concentration in rats naïve for ethanol as well as in rats daily administered with repeated ethanol injections that were not paired with the cue. It appears probable that these conditioned responses by extracellular glutamate concentrations may participate in the environmental cue-induced conditioned cravings for ethanol that are thought to be related to the high frequency of relapse in detoxified alcoholics.

Risk Factors for Parkinson’s Disease: The Leisure World Cohort Study

We conducted a case-control study nested within a prospective cohort study of 13,979 residents of Leisure World Laguna Hills, a retirement community in southern California, for etiologic clues for Parkinson's disease (PD). Between 1981 (when first mailed a health survey) and 1998, we identified 395 PD cases from death certificates, hospital discharge diagnoses and a 1992 follow-up questionnaire. Six controls were individually matched on sex, birth date (+/-2 years), vital status and, if dead, death date (+/-1 year) to each case. Baseline characteristics of the 395 cases and 2,320 controls were analyzed as potential PD risk factors. The risk of PD was significantly reduced among smokers, hypertensives, coffee drinkers and alcohol consumers, and significantly increased among those with 3 or more children and with a high intake of total vitamin A and dietary vitamin C. The multivariate odds ratios (95% confidence intervals) were 0.42 (0.22-0.80) for current cigarette smokers of 1+ pack/day, 0.62 (0.48-0.80) for current users of hypertensive medication, 0.71 (0.52-0.95) for coffee drinkers of 2+ cups/day and 0.77 (0.58-1.03) for drinkers of 2+ alcoholic drinks/day. Risk increased with increasing number of children (1.25 for 1, 1.34 for 2 and 1.90 for 3+ children; p for trend = 0.0003). The increased risks among individuals in the highest third of total vitamin A intake and of dietary vitamin C intake were no longer statistically significant after adjusting for the other variables. These findings suggest several environmental factors that may be related to the development of PD and support a multifactorial etiology.

Effects of alcohol on brain-derived neurotrophic factor mRNA expression in discrete regions of the rat hippocampus and hypothalamus

Chronic alcohol consumption has adverse effects on the central nervous system, affecting some hippocampal and hypothalamic functions. In this study we tempted to demonstrate that some of these modifications could involve impairment of neurotrophic factors. Three experimental groups of male Sprague Dawley rats were studied: one control group, one chronically treated with alcohol vapor according to a well-established model that induces behavioral dependence, and a third group treated similarly but killed 12 hr after alcohol withdrawal. In all groups, changes in brain-derived neurotrophic factor mRNA expression occurring in the hippocampus and supraoptic nucleus were first analyzed by reverse transcription-polymerase chain reaction and then by in situ hybridization. In parallel, we used ribonuclease protection assay to measure mRNA levels encoding trkB in the two central nervous system regions. We showed that chronic alcohol intoxication decreases brain-derived neurotrophic factor mRNA expression in discrete regions of the rat hippocampus (CA1 region and dentate gyrus) and in the supraoptic nucleus of the hypothalamus. We also showed a global up-regulation of trkB mRNA expression encoding the high-affinity brain-derived neurotrophic factor receptor (TrkB), after applying the same treatment. Following 12 hr of alcohol withdrawal, a significant increase in BDNF mRNA expression was observed in the dentate gyrus and CA3 region of hippocampus and in the hypothalamic supraoptic nucleus. These findings suggest that chronic alcohol intake may modify hippocampal and hypothalamic neuronal functions through modifications in growth factors and its receptors.

Ethanol induces taurine release in the amygdala: an in vivo microdialysis study

The effect of acute IP ethanol injections on the extracellular aspartate, glutamate, taurine and GABA content of the basolateral amygdala microdialysate was investigated in relationship with total brain ethanol. Each acute intraperitoneal injection of ethanol, 0.5, 1.0, 2.0 and 3.0 g/kg body weight, induced an immediate increase in microdialysate taurine; both 0.5 and 1.0 g/kg ethanol evoked an increase during the first 20 minutes following injection which returned to baseline value by 40 minutes, despite the fact that ethanol was detectable in the brain until 60 or 120 minutes, respectively. After either 2.0 or 3.0 g/kg ethanol there was an increase in taurine of gradual intensity which gradually declined to reach baseline values by 100 minutes. In contrast, the ethanol concentration for 2.0 g/kg remained elevated at the end of the 120 minutes; approximately 25 mg ethanol/mg protein. The stimulated release of taurine within the amygdala could participate in the regulation of ethanoli-nduced changes in osmolarity, since taurine is postulated to act as an osmoregulator in the brain. Taurine could also mediate or interact with ethanol-induced central nervous system effects, as it exerts a modulatory action on cell excitability and neurotransmitter processes.

Ethanol, GABA and epilepsy

Ethanol exerts its behavioral effects largely by interacting with receptors to brain neurotransmitters. The molecular mechanisms involving these interactions are still not well known since an ideal model for their study is currently unavailable. In addition, responses to alcohol may vary due to factors such as genetic predisposition, ethanol concentration consumed, and stimuli such as stress, socialization, etc. The chronic consumption of alcohol, similar to that of other drugs such as benzodiazepines and barbiturates, is linked to GABAergic neurotransmission. GABA is the predominant inhibitory neurotransmitter in the brain. In a context of substance abuse, these three drugs first cause a gratifying effect, later tolerance and finally, physical and psychological dependence. If consumption is interrupted abruptly, a withdrawal syndrome occurs. The Alcohol Withdrawal Syndrome (AWS) is a state of hyperexcitability characterized by anxiety, fear, muscular rigidity and tonic-clonic seizures with epileptiform-type characteristics. The epileptic seizures seen during AWS are often similar to those seen in experimental epilepsy models such as "kindling" or GABA Withdrawal Syndrome (GWS) models. A possible correlation between these models and AWS will allow for a better understanding of the cellular and molecular effects that alcohol exerts on the brain.

Discriminative stimulus effects of ethanol: neuropharmacological characterization

Generally, compounds discriminated by animals possess psychotropic effects in animals and humans. As with many other drugs of abuse, strength of the ethanol discriminative stimulus is dose related. The majority of studies show that doses close to 1.0 g/kg are close to the minimum at which the discrimination can be learned easily. Substitution studies suggest that anxiolytic, sedative, atactic, and myorelaxant effects of ethanol all play an important role in the formation of its intercoeptive stimulus. Low doses of ethanol produce more excitatory cues, similar to amphetamine-like subjective stimuli, whereas higher doses produce rather sedative/hypnotic stimuli similar to those elicited by barbiturates. Substitution studies have shown that the complete substitution for ethanol may be exerted by certain GABA-mimetic drugs acting through different sites within the GABA(A)-benzodiazepine receptor complex (e.g., diazepam, pentobarbital, certain neurosteroids), gamma-hydroxybutyrate, and antagonists of the glutamate NMDA receptor. Among the NMDA receptor antagonists both noncompetitive (e.g., dizocilpine) and competitive antagonists (e.g., CGP 40116) are capable of substituting for ethanol. Further, some antagonists of strychnine-insensitive glycine modulatory sites among the NMDA receptor complex (e.g., L-701,324) dose-dependently substitute for the ethanol discriminative stimulus. On the other hand, neither GABA-benzodiazepine antagonists nor NMDA receptor agonists produce contradictory effects (i.e., reduce the ethanol discriminative stimulus). There is influence of a particular training dose of ethanol on the substitution pattern of different compounds. For example, 5-HT(1B/2C) agonists substitute for intermediate (1.0 g/kg) but not higher (2.0 g/kg) ethanol training doses. Discrimination studies with ethanol and drugs acting on NMDA and GABA receptors consistently indicate asymmetrical generalization. For example, ethanol is able to generalize to barbiturates and benzodiazepines, but neither the benzodiazepine nor barbiturate response generalizes to ethanol. Only a few drugs are able to antagonize, at least to some extent, the discriminative stimulus of ethanol (e.g., partial inverse GABA-benzodiazepine receptor antagonist Ro 15-4513 and the opioid antagonist naloxone). The ethanol stimulus effect may be increased (i.e., stronger recognition) by N-cholinergic drugs (nicotine), dopaminergic drugs (apomorphine), and 5-HT3 receptor agonists (m-chlorophenylbiguanide). Thus, the ethanol stimulus is composed of the several components, with the NMDA receptor and GABA(A) receptor complex being of particular importance. This suggests that a drug mixture may be more capable of substituting for ethanol (or block its stimulus) than a single compound. The ability of drugs to substitute for the ethanol discriminative stimulus is frequently, although not preclusively, associated with the reduction of voluntary ethanol consumption. The examples of positive correlation are gamma-hydroxybutyrate, possibly memantine and certain serotonergic drugs such as fluoxetine. However, it remains uncertain to what extent the discriminative stimulus of ethanol can be seen as relevant in the understanding of the complex mechanisms of dependence.

Effect of ethanol on chromatin and nonhistone nuclear proteins in rat brain

Changes in chromatin conformation and nonhistone nuclear protein composition were analyzed in various classes of nuclei from the brain of control and chronic ethanol fed rats. Conformational studies of chromatin by circular dichroism spectrophotometry showed an increased molar ellipticity [theta] of chromatin in neuronal, astrocyte and oligodendroglial nuclei due to ethanol treatment. The increased molar ellipticity directly indicates relaxed state of chromatin in these nuclei, which facilitates ready state of transcription and replication. Further, the circular dichroism spectrum, due to a change over point at approximately 260 nm also indicated the possibility of DNA-protein interactions governing chromatin conformation. In microglial nuclei, the circular dichroism spectrum showed a decrease in molar ellipticity due to ethanol treatment, indicating the existence of chromatin in a condensed state. This type of circular dichroism change points towards the possibility of closed conformation, which renders the gene sequences not accessible due to conformational constrains of the chromatin. Since circular dichroism changes indicated the involvement of DNA-protein interactions, changes in nonhistone nuclear proteins were analyzed in these classes of nuclei by two-dimensional gel electrophoresis. In astrocytes and oligodendrocytes two new proteins appeared in each type of nuclei while in neurons and microglial nuclei four different proteins were either completely missing or showed a decrease. These changes indicate the presence of dynamic flux of nonhistone nuclear proteins in chromatin. Taken together, the changes in chromatin conformation, associated with specific changes in non histone nuclear protein composition suggest the modulation of chromatin as a response to ethanol evoked stimulus and has relevance in the regulation of cellular responses to ethanol crisis in brain.

Ethanol-reinforced behaviour in the rat: effects of uncompetitive NMDA receptor antagonist, memantine

Ethanol has been reported to alter NMDA receptor-mediated biochemical and electrophysiological responses in vitro. The aim of the present study was to evaluate the effects of an uncompetitive NMDA receptor antagonist memantine, in animal models of alcoholism. Male Wistar rats were trained to drink 8% ethanol in a free-choice, limited access procedure. A separate group of animals was trained to lever press for 8% ethanol in an operant procedure where ethanol was introduced in the presence of sucrose. The selectivity of memantine's actions was assessed by studying its effects on food or water consumption in separate control experiments. Memantine (4.5-24 mg/kg) significantly, but not dose dependently, affected ethanol drinking in the limited access procedure. However, only 6 mg/kg memantine selectively decreased ethanol drinking. Memantine did not alter ethanol intake in rats trained to lever press for ethanol in the operant procedure. Only 9 mg/kg memantine reduced operant responding in the extinction procedure in the rats trained to lever press for ethanol. The same dose of memantine significantly reduced the operant behaviour of rats trained to respond for water. These results indicate that: (i) single doses of memantine only moderately and not dose dependently reduce alcohol drinking in the limited access procedure; (ii) memantine produces non-selective effects on operant behaviour in rats trained to lever press for ethanol in an oral self-administration procedure.

Reduced levels of GABA-benzodiazepine receptor in alcohol dependency in the absence of grey matter atrophy

BACKGROUND

We tested the hypothesis that reduced levels of the GABA-benzodiazepine receptor occur in alcohol dependency using single photon emission tomography (SPET) and the specific GABA-benzodiazepine ligand, 123I-iomazenil.

METHOD

Neurologically and cognitively unimpaired abstinent alcohol-dependent (n = 12) and non-alcohol-dependent male subject (n = 14) underwent a 123I-iomazenil SPET scan. SPET and magnetic resonance images were co-registered and voxel-based statistical tests performed. Subjects' clinical and alcohol history were obtained with standard questionnaires. The relationships between clinical and alcohol variables and the regional level of GABA-benzodiazepine receptors were investigated using multiple regression analysis.

RESULTS

Abstinent alcohol-dependent subjects had decreased levels of GABA-benzodiazepine receptor compared with non-alcohol-dependent subjects within the frontal, parietal and temporal cortices, including regions in which grey matter atrophy was absent.

CONCLUSIONS

Alcohol dependency is associated with reduced GABA-benzodiazepine receptor levels in the absence of grey matter atrophy in some cortical regions, such as within the parietal lobe. Regional variability of reduction in GABA-benzodiazepine receptors demonstrates that alcohol does not have a global, toxic effect on the brain.

Effect of acute, but not chronic ethanol treatment on somatostatin secretion in rat hypothalamic neurons

To examine the possible involvement of somatostatin in growth hormone modifications induced by ethanol, we examined: (1) the effects of chronic ethanol exposure of cultured hypothalamic neurons on somatostatin content and mRNA levels; (2) the acute effect of ethanol on somatostatin release stimulated by N-methyl-D-aspartate (NMDA). The results showed that 8 days of ethanol exposure (10-100 mM) did not decrease somatostatin content or somatostatin mRNA levels. Ethanol treatment alone had no significant effect on cell morphology or on protein content. In contrast, acute application of ethanol in 8 day-old cultures significantly reduced (50 mM) or completely blocked (100 mM) somatostatin release elicited by 50 microM NMDA without modifying basal release. We conclude that chronic ethanol treatment to concentrations up to 100 mM has no effect on somatostatin biosynthesis in fetal rat hypothalamic neurons, while weaker concentrations decrease NMDA-induced somatostatin release.

Functional characterization of a kindling-like model of ethanol withdrawal in cortical cultured neurons after chronic intermittent ethanol exposure

Chronic ethanol exposure has been reported to alter NMDA and GABA(A) receptor function and gene expression in brain regions of animals and mammalian cultured cortical neurons. In the present study, we investigated the effects of another model of chronic, but intermittent, ethanol treatment (CIE) on GABA(A) and NMDA receptor systems in cortical neurons. CIE (50 mM ethanol, 12 h exposure/12 h withdrawal, 5 cycles) exposure produced increased [3H]MK-801 binding and diazepam insensitive binding sites as measured by [3H]Ro15-4513 binding to cortical cultured neuronal membranes, at 0 h following the last treatment cycle relative to control neurons. The NMDA mediated increase in intracellular calcium [Ca2+]i was also increased following similar CIE treatment. CIE treatment also increased the ability of pentylenetetrazol (PTZ) to inhibit GABA mediated 36Cl- influx relative to control neurons. These effects were not reversible following 1 week ethanol withdrawal, implying enhanced sensitivity of PTZ to inhibit GABA(A) receptor mediated inhibition, and an increased NMDA receptor function in CIE treated cortical neurons. These alterations are consistent with the behavioral studies in animals, and suggest that both GABA(A) and NMDA receptors play an important role in ethanol withdrawal following either chronic or CIE exposure. Furthermore, this provides a feasible in vitro model for further biochemical and molecular studies of the mechanism underlying the CIE induced kindling-like phenomenon observed in humans.

Basic aspects of GABA-transmission in alcoholism, with particular reference to GABA-transaminase

Neuronal dysfunction is the neurobiological basis for alcoholic behaviour, and ethanol craving seems related to hypofunction of the GABA-ergic activity. Gamma-aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the central nervous system (CNS). In several studies, GABA has been shown to be an important target of ethanol in the CNS, partly, as a consequence of damage to membrane-bound enzymes and receptors. GABA is involved in mediating pre- and post-synaptic inhibition of neuronal activity. It is speculated that the initial excitatory effects of ethanol may be due to inhibition of GABA-ergic activity whereas the sedative effects of the higher doses may be mediated by the activation of this inhibitory system. In the CNS, GABA is synthesised from glutamic acid by the enzyme glutamate decarboxylase (GAD) and catabolized into succinic semialdehyde by the enzyme GABA-transaminase (GABA-T), which are pyridoxal phosphate (PLP) dependent enzymes. Platelet GABA-T was characterized as being similar to central GABA-T. Inhibition of GABA-T with certain potent and selective compounds markedly increases the levels of brain GABA. Experimentally, acute ethanol treatment does not alter GABA-T activity whereas chronic treatment produces an increase in the activity, though, with some reservations since a bimodal effect has been found in chronically ethanol-treated rats. Thus, as it will be discussed below, it may be suggested that GABA-T inhibitors (e.g. vigabatrin) could have a potential role in the treatment of alcoholism and in some of the problems of ethanol withdrawal and of other drugs of abuse. Related studies on metabolism and concentrations of GABA are also promising and show a greater increase in our understanding of the aetiology and treatment of ethanol dependence and withdrawal. In general, this article also reviews both the animal and clinical observations in the field of alcoholism with regard to the GABA system.

Brain GABA metabolism after chronic ethanol consumption and withdrawal in rats

We have studied the activities of the GABA metabolizing enzymes-GABA aminotransferase (GABA-AT), succinic semialdehyde dehydrogenase (SSA-DH) and SSA reductase (SSA-R) and the levels of GABA, glutamine and glutamate in rats preferring water (WP) or ethanol (EP) after 6 months of ethanol consumption and 12 hours to 7 days after withdrawal. We showed decreased GABA levels in the brain stem, decreased GABA-AT activity in the hemispheres and brain stem, and enhanced GABA-AT activity in the striatum of EP rats compared with the control or WP animals following chronic consumption of ethanol. We found decreased activity of SSA-R and SSA-DH in the hemispheres and brain stems of alcohol-treated rats compared to the control rats. Withdrawal (0.5-7 days) induced numerous profound changes in GABA metabolism.

Effects of chronic ethanol treatment and ethanol withdrawal on [3H]SCH23390 binding to rat striatal membranes

The effects of chronic ethanol administration and ethanol withdrawal on the kinetic and pharmacological properties of [3H]SCH23390 binding sites and the labelling of central dopamine D-1 receptors were studied in the striatum of the rat. Chronic 40 day ethanol treatment produced a statistically significant decrease (p < 0.05) in maximum binding (Bmax) on striatal dopamine D-1 receptors of the rat, KD remaining unaltered. The withdrawal of ethanol did not affect the kinetic binding parameters. The rank order of potency in displacing the specific [3H]SCH23390 binding of several dopamine antagonists, agonists and serotonin-related drugs was consistent with the pharmacological profile of dopamine D-1 receptors. Chronic ethanol treatment led to a statistically significant increase in receptor affinity (lower Ki than controls) for (+)-butaclamol (p < 0.05). Ethanol withdrawal for 24 hr increased the affinity of [3H]SCH23390-labeled binding sites for norepinephrine. The addition of 0.03-0.68 M ethanol in vitro had no significant effects on [3H]SCH23390 binding in striatal preparations taken from both control and ethanol-treated rats. The results show that rat striatal [3H]SCH23390-labelled binding sites are affected by different conditions of ethanol exposure, possibly suggesting the medication of striatal dopamine pathways in the responses to ethanol intoxication.

Chronic ethanol ingestion produces cholinergic hypofunction in rat brain

Alterations in cholinergic function due to prolonged ethanol exposure (up to 9 months) were assessed by choline acetyltransferase (ChAT) activity and high-affinity choline uptake (HAChU) in three brain regions of the Long-Evans rat: frontal cortex, parietal cortex, and region of the nucleus basalis of Meynert (NbM). No statistically significant changes were found in ChAT activity in the 3-month group; however, ChAT activity was decreased in both the frontal cortex (-32%) and NbM region (-22%) after 6 months of ethanol exposure. ChAT activity in the parietal cortex was increased 30% after 6 months. Nine months of exposure significantly decreased ChAT activity in all three brain regions. No significant differences were observed in high-affinity choline uptake after 3 months of ethanol exposure. However, after 6 months of ethanol exposure HAChU was decreased to 51% of control values in the frontal cortex. There was a simultaneous increase in HAChU to 43% and 178% of control values in the NbM and parietal cortex, respectively. However, choline uptake was significantly decreased in the frontal cortex and NbM region after 9 months of exposure. The results indicate a neurotoxic effect of prolonged intake of ethanol on the basal forebrain cholinergic projection system, which may cause impairment of cholinergic innervation of target areas of the basal nucleus complex.

5-HT3 receptor antagonist, tropisetron, does not influence ethanol-induced conditioned taste aversion and conditioned place aversion

Numerous works have demonstrated an interaction between 5-HT3 receptor antagonists and some of the effects of ethanol (EtOH) using biochemical, electrophysiological, and behavioral techniques. Thus 5-HT3 antagonists are capable of reducing EtOH-induced release of dopamine in the nucleus accumbens, EtOH-induced hyperlocomotion, and voluntary EtOH consumption in laboratory animals. In addition to its rewarding effect, EtOH possesses aversive properties as demonstrated in the conditioned taste aversion (CTA) and conditioned place aversion (CPA) paradigms. The role of 5-HT3 receptors in aversive effects of EtOH remains, however, unknown. We decided to study the effect of 5-HT3 antagonist, tropisetron, on aversive properties of EtOH (1.5 g/kg i.p.) in rats using the CTA and CPA models. In addition, effect of tropisetron on morphine (Mf)-induced CTA (10.0 mg/kg SC) was investigated. Tropisetron (0.001-0.5 mg/kg) did not influence CTA produced by EtOH and Mf. When given alone, it failed to produce any taste conditioning. Furthermore, tropisetron did not modify CPA induced by EtOH. Our results suggest that 5-HT3 receptors are not involved in aversive effects of acute doses of EtOH.

Ethanol- and diazepam-induced cytochrome oxidase activity in mammillary bodies

This study aims to analyze the effect of the administration of diazepam and alcohol on cytochrome c oxidase activity (COX) in the mammillary bodies (MB) with a quantitative densitometry method. The histochemical reaction of the COX is used as a reflection of energy consumption. Our results show an increase in the COX activity after treatment with diazepam in the different nuclei of MB: medial medial nucleus (MMNm), lateral medial nucleus (MMN1), and lateral nucleus (LMN) of the MB, the MMNm and LMN being significantly more active compared to the MMN1. Furthermore, the consequences of administering these drugs become manifest in spatial learning (water T maze). The performance in a spatial discrimination task did not prove to be impaired.

Taurine increases in the nucleus accumbens microdialysate after acute ethanol administration to naive and chronically alcoholised rats

The extracellular changes of amino acids (glutamate, taurine and GABA) in the nucleus accumbens of freely moving rats were estimated using the microdialysis technique following acute and chronic ethanol injections (1, 2, and 3 g/kg body weight). Compared to baseline values, taurine increased by 154% +/- 73%, 142% +/- 40% and 162% +/- 75% 20 min after the acute injection of respectively, 1, 2, and 3 g/kg body weight ethanol, while 40 min after ethanol injection, taurine had increased by 124% +/- 36%, 146% +/- 54% and 168% +/- 98%. No changes in either glutamate or GABA were detected at any time points assayed. In the rats which had received chronic ethanol administration prior to a further acute ethanol injection (1, 2, and 3 g/kg body weight), taurine increased by 138% +/- 73%. 144% +/- 39% and 180% +/- 85% 20 min after the ethanol injection at 40 min post ethanol injection taurine had increased by 134% +/- 44%, 160% +/- 56% and 158% +/- 45%, compared to the basal baseline value. No significant changes were observed in either glutamate or GABA microdialysate content in these chronic studies. The biological role played by taurine after acute ethanol injection in the nucleus accumbens remains unclear but may be associated with a yet, undefined mechanism, in reducing the cytotoxicity of ethanol.

Modulation of tryptophan hydroxylase activity in vitro by ethanol depends on biopterin cofactor concentration

The mechanism of ethanol action at serotonergic neuronal systems in the brain was investigated by examining the effects of alcohols on the activity of tryptophan hydroxylase (TPH) in vitro using natural type of biopterin as cofactor. Alcohols inhibited the activity of TPH prepared from rat brain in a noncompetitive manner with respect to both the biopterin cofactor and the L-tryptophan substrate. The rank order of inhibitory potency of the tested alcohols was n-propanol > iso-propanol > ethanol > methanol. The kinetic study indicated that alcohols more potently affected the enzyme interaction with cofactor than substrate. Ethanol, at concentrations that can be reasonably attained in vivo (i.e., 25-100 mM) significantly decreased TPH activity in the presence of a physiological concentration of cofactor. However, the reduction was only approximately 5% of control activity, because Ki, values of ethanol for the enzyme were very high (800-1000 mM). From the present results, it was concluded that the direct inhibition of the synthetic enzyme itself by ethanol would contribute little to in vivo effects of ethanol on serotonergic neuronal systems.

The 5-HT1A receptor agonist 8-OH-DPAT reduces ethanol intake and maintained behavior in female Sprague-Dawley rats

Agents affecting serotonergic (5-hydroxytryptamine, 5-HT) function influence ethanol consumption in rats and primates. In the present study female Sprague-Dawley rats were trained to orally self-administer 8% ethanol (v/v) in a large operant chamber in a 60-min test period by a prandial drinking technique. The number of response, ethanol reinforcers (dipper deliveries), and ethanol consumption (g/kg) were measured following administration of the 5-HT1 A agonist 8-OH-DPAT (0.001 1.0 mg/kg, ip) 30 min prior to testing. Locomotor activity (LMA) was also measured to assess activity changes induced by 8-OH-DPAT. 8-OH-DPAT selectively reduced ethanol ingestion from 17.1 +/- 3.2 dipper deliveries under vehicle conditions to 6.6 +/- 3 at a dose of 0.1 mg/kg. Higher doses of 8-OH-DPAT (0.5 and 1.0 mg/kg) significantly reduced both ethanol ingestion and LMA. Lower doses of 0.001-0.01 mg/kg of 8-OH-DPAT were without effect on ethanol intake and maintained behavior. These results demonstrate that, under the present experimental conditions, the 5-HT1A receptor agonist 8-OH-DPAT reduced ethanol self-administration in the rat, and support a role for 5-HT1A receptors in the mediation of ethanol reinforcement.

Studies on the role of 5-HT3 receptors in the mediation of the ethanol interoceptive cue

The drug discrimination test was used to evaluate the role of 5-HT3 receptors in the mediation of the stimulus properties of ethanol in rats trained to discriminate between ethanol (1.0 g/kg, 10% v/v, i.p.) and saline vehicle. Rats trained to discriminate between a lower dose of ethanol (0.5 g/kg i.p.) failed to attain discrimination criteria after 20 weeks (100 sessions) of training. None of the doses of 5-HT3 receptor antagonists (0.001, 0.01, 0.1, 1.0, 10.0 mg/kg of tropisetron or ondansetron) administered i.p. 30 min before ethanol, antagonized the discriminative stimulus properties of ethanol. Furthermore, none of the centrally (1, 10, 35 micrograms per rat) or i.p. (0.1, 1.0, 2.5, 5.0, 10.0 mg/kg) administered doses of 5-HT3 receptor agonist, 1-(m-chlorophenyl)-biguanide, could replace the ethanol discriminative cue. These results suggest that 5-HT3 receptors are not primarily involved in the mediation of the stimulus properties of ethanol.

Positron emission tomographic studies of cerebral benzodiazepine-receptor binding in chronic alcoholics

Positron emission tomography was used with [11C]flumazenil (FMZ) and [18F]fluorodeoxyglucose to study GABA type A/benzodiazepine (GA-BA-A/BDZ) receptors and cerebral metabolic rates for glucose (1CMRg1c) in 17 male patients with severe chronic alcoholism (ALC), 8 with (ACD) and 9 without alcoholic cerebellar degeneration (non-ACD). In comparison with male normal controls of similar ages, the ALC group had significantly reduced FMZ ligand influx (K1), FMZ distribution volume (DV), and 1CMRg1c bilaterally in the medial frontal lobes, including superior frontal gyrus and rostral cingulate gyrus; the ACD group had significant reductions of K1, DV, and 1CMRg1c bilaterally in the same distribution, and also in the superior cerebellar vermis; and the non-ACD group had significant reductions of K1, DV, and 1CMRg1c bilaterally in the same regions of the frontal lobes but not in the superior cerebellar vermis. When compared with the non-ACD group, the ACD group had significant reductions of K1, and DV bilaterally in the superior cerebellar vermis. The results suggest that severe chronic alcoholism damages neurons containing GA-BA-A/BDZ receptors in the superior medial aspects of the frontal lobes, and in patients with clinical signs of ACD, neurons containing GABA-A/BDZ receptors in the superior cerebellar vermis.

Serotonergic ethanol effects and auditory evoked dipole activity in alcoholic and healthy subjects

Ethanol has central serotonergic effects that may be of pathogenetic importance in a subgroup of alcohol-dependent patients with a central serotonergic hypofunction. Recent results indicate that pronounced amplitude increases of auditory evoked responses (tangential dipoles, N1/P2 component) with increasing stimulus intensity (loudness) may be an indicator of such a low serotonergic neurotransmission. Because of its serotonin-agonistic effects, ethanol can be expected to decrease this intensity dependence. Twenty-eight alcoholic patients were studied both in the intoxication phase and after 1 week of withdrawal. A reduced intensity dependence of the tangential dipole activity was observed in the intoxicated state. Correspondingly, a reduction of this parameter was found in 14 healthy subjects after an ethanol load (1 g/kg, p.o.).

Effects of an acute dose of ethanol on dopaminergic and serotonergic systems from rat cerebral cortex and striatum

Intraperitoneal injection 10 min before sacrifice of 1.5 g ethanol/kg weight produced an increase in rat striatal levels of homovanillic acid (HVA) (p < 0.05) but did not affect the striatal concentrations of dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC), serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA). A similar ethanol treatment led to decreases in 5-HT (p < 0.05) and 5-HIAA (p < 0.05) from cerebral cortex (prefrontal and anterior cingulate areas). The results point to several ethanol-linked alterations in central serotonergic and dopaminergic systems.

Single-dose ritanserin and alcohol in healthy volunteers: a placebo-controlled trial

A double blind cross-over design trial was carried out to investigate the effect of simultaneous administration of alcohol (0.5 g/kg) and ritanserin (10 mg) on biological and behavioral functioning. Twenty healthy volunteers were selected to participate in the study. To assess the effect of treatments the following evaluations were performed: psychomotor tests, vital signs, intoxication, euphoria, and mood. In addition, ritanserin and alcohol plasma concentration were measured. Psychomotor performance and vital signs during the ritanserin session did not differ significantly from the placebo session. Similar results were obtained in regard to alcohol intoxication, euphoria, and mood, except for tiredness and alertness, which were significantly different compared to placebo. Differences in blood alcohol concentration between the ritanserin and the placebo sessions did not attain significance. Plasma ritanserin concentration was 143 ng/ml 1 h after alcohol administration and decayed to 53 ng/ml 6 h after alcohol consumption in the active treatment session. Our findings tend to indicate that ritanserin neither enhances the central nervous system depressant effect of alcohol nor produces a pharmacokinetic interaction during acute alcohol ingestion.

Pharmacotherapy and psychotherapy for the treatment of alcoholism in Germany

Although past alcoholism treatment in Germany has primarily focused on psychotherapy, new advances in pharmacotherapy are expanding therapeutic options. Recent biomedical studies have produced new theories about how alcohol affects neurotransmitters in the brain. These studies have led to new pharmacologic strategies for the treatment of alcoholism using dopamine agonists and antagonists, serotoninergic agents, glutamate antagonists, and opiate antagonists. While preliminary studies of these agents offer encouraging results, it remains to be demonstrated which agent(s) will provide effective pharmacotherapy for this disease.

Autoradiographical study of types 1 and 2 of benzodiazepine receptors in rat brain after chronic ethanol treatment and its withdrawal

The effect of chronic ethanol treatment, and its withdrawal on benzodiazepine binding sites in rat brain is described in this autoradiographical study using the benzodiazepine agonist [3H]flunitrazepam. Several areas of the rat cerebral cortex, hippocampus, mesencephalon, cerebellum and lateral geniculate nucleus were studied in animals, chronically treated with ethanol, and 24 or 48 hr after ethanol withdrawal. The [3H]flunitrazepam binding and the relative percentages of binding to BZ1 and BZ2 sites, using zolpidem as a BZ1 site inhibitor, are described. The cerebellum and red nucleus, which only express BZ1 binding sites, appear to be areas significantly modified by ethanol and its withdrawal. In no other structure did ethanol modify [3H]flunitrazepam binding nor change the relative percentage of BZ1 and BZ2 sites.

Simultaneous changes in striatal dopamine, serotonin, and metabolites after withdrawal seizures in rats from dependence on alcohol

Ethanol dependence was achieved in male, Long-Evans rats after 8 days on a balanced liquid diet that supplied 4.5% ethanol. After 1-h access to a solution of 10% ethanol (95%)/5% sucrose, the rats were deprived of food, water, and ethanol for 9 h. Following 30-s key jingling, about 80% of the animals exposed to ethanol experienced tonic-clonic seizures. Neurochemical analyses of striatal tissues revealed a significant (p < 0.05) increase in dopamine (DA) and a significant decrease in serotonin (5-HT) in the ethanol-exposed rats that had seizures compared to control rats. Homovanillic acid concentrations of the ethanol-treated rats with seizures were significantly higher than the levels found in ethanol-treated animals that had experienced no seizures. Daily average ethanol intake of the rats that had seizures vs. those that did not was almost the same at 16 g/kg/day. The findings indicate that rats experiencing ethanol withdrawal-induced seizures manifest opposite alterations in dopaminergic and serotoninergic activity compared to controls. The present results do not reveal if the striatal changes are caused by ethanol rather than by the seizures.

Basic aspects of GABA-transaminase in neuropsychiatric disorders

Over the last two decades, there have been several studies suggesting the major inhibitory amino acid neurotransmitter gamma-aminobutyric acid (GABA) is involved directly and/or indirectly in the pathogenesis of many neurologic diseases and psychiatric disorders. GABA is mainly degradated to succinic semialdehyde in a reaction catalyzed by the enzyme GABA-transaminase (GABA-T). Inhibition of this enzyme produces considerable elevation of GABA contents in the brain, and such elevation has been found to correlate with pharmacologic and behavioral effects. We focus attention, from the basic aspects, on brain and platelet GABA-T activities in various species, with a special reference to neuropsychiatric disorders. It seems that the activity of GABA-T in the brain and/or in the blood platelets is correlated to certain neuropsychiatric disorders such as alcoholism, epilepsy, and Alzheimer's disease. In animal and human studies, platelet GABA-T was identified with similar kinetic and inhibitor characteristics to those of the brain. Therefore, in this way, studies of the activity of the enzyme GABA-T in relation to neuropsychiatric disorders could be undertaken to understand, diagnose, and treat GABA-related disorders of the central nervous system.

Alcohol drinking in rats injected ICV with 6-OHDA: effect of 8-OHDPAT and tropisetron (ICS 205930)

6-Hydroxydopamine (6-OHDA) was administered ICV to Wistar male rats. Lesioned animals displayed lower preference for ethanol (ETOH) than sham-operated rats. Among 6-OHDA lesioned rats only 9% became high-preferring whereas 20% of sham-operated animals became high-preferring ones. Both tropisetron (the antagonist of 5-HT3 receptors) and 8-OHDPAT (the 5-HT1A receptor agonist) reduced ETOH drinking in high-preferring rats. However, in 6-OHDA lesioned rats the effect of tropisetron was reduced although 8-OHDA retained its effect on ETOH consumption. These results suggest that brain DA neurons are involved in tropisetron action but are not responsible for antipreference effect of 8-OHDPAT.

Novel synergistic treatment of ethanol withdrawal seizures in rats with dopamine and serotonin agonists

A recent observation in this laboratory of a simultaneous increase in striatal dopamine and a decrease in serotonin in ethanol-dependent rats during ethanol withdrawal prompted studies with combined dopaminergic + serotoninergic agonists to stop withdrawal seizures. Amphetamine (2 mg/kg) + fenfluramine (8 mg/kg) given jointly, but not separately, prevented ethanol withdrawal seizures as effectively as benzodiazepines (chlordiazepoxide), the current drugs of choice. The combination of amphetamine and fenfluramine, unlike chlordiazepoxide, significantly reduced intake of ethanol during and immediately following ethanol withdrawal.

Effect of chronic treatment with ethanol and withdrawal of ethanol on binding of [3H]SCH23390 to D1 dopamine receptor in rat visual cortex and hippocampus. An autoradiographic study

Male Wistar rats, treated with ethanol for 8 weeks and pair-control animals, were used to study the effects of chronic treatment with ethanol, and withdrawal of ethanol for 24 and 48 hr on [3H]SCH23390 binding. The visual cortex (Laminae III-IV and Lamina VI), the superficial grey layer of the superior colliculus, and the molecular layer of the dentate gyrus of the hippocampus were the cerebral areas analysed. Non significant changes were observed in hippocampus and Laminae III-IV of the visual cortex after treatments with alcohol. More interesting results were obtained from Lamina VI, where the chronic treatment with ethanol did not modify the binding of [3H]SCH23390, whereas the withdrawal of ethanol produced a statistically significant increase in binding values. In addition, superficial grey layer of the superior colliculus showed a significant increase in binding values between 48 hr withdrawal and ethanol treated groups. The results herein reported suggest that some structures involved in visual functions are related to responses of adaptation to ethanol.

Serotonergic neurons in the alcohol preferring rats

Previously, we have shown that the serotonin (5-HT) content and fiber density in a number of terminal brain regions have been found to be decreased in the selectively bred, alcohol preferring (P) rats than in the alcohol nonpreferring (NP) rats. In this study, we further report that, compared with NP rats, there were fewer 5-HT-immunostained (5-HT-IM) neurons in the major ascending raphe nuclei of the P rats. Among the three major groups of 5-HT neurons responsible for the majority of ascending projections to forebrain, dorsal raphe (B7), median raphe (B8), and B9, there were fewer 5-HT-IM neurons in the median and dorsal raphe (not including nucleus oralis) of P rats, compared with NP rats (unpaired Student's test). No difference was observed in the B9 group. When the animals were treated with pargyline and L-tryptophan to enhance the 5-HT in the neurons, the number of 5-HT-IM neurons increased in both lines of rats. However, the difference in the number of 5-HT neurons between the rat lines remained. The intensity of 5-HT-IM was also found to be lower in the dorsal raphe neurons of the untreated P than in the untreated NP rats. The decreased 5-HT-IM was supported by high performance liquid chromatography measurement of 5-HT content, which also indicated that 5-HT content of the dorsal raphe was lower in the P than in the NP rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Alcohol drinking in rats treated with 5,7-dihydroxytryptamine: effect of 8-OH-DPAT and tropisetron (ICS 205-930)

5,7-Dihydroxytryptamine (5,7-DHT) was administered ICV to Wistar male rats. Lesioned rats displayed higher preference for ETOH than sham-lesioned animals. Among 5,7-DHT-pretreated rats 38% became high-preferring, while only 22% of sham-lesioned rats displayed this behavioural pattern (p < 0.05). Both 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT; the agonist of serotonin 5-HT1A receptors) and tropisetron (ICS 205-930, the antagonist of 5-HT3 receptors) reduced ETOH consumption in high-preferring, sham-lesioned rats. However, in 5,7-DHT rats the effect of 8-OH-DPAT was completely abolished, while tropisetron retained its antipreference activity. Therefore, it seems that 5-HT1A autoreceptors are critically involved in 8-OH-DPAT action, while 5-HT3 receptor sites responsible for tropisetron action are located beyond the 5-HT system.

Stereological study of the ultrastructural changes induced by chronic alcohol consumption and dehydration in the supraoptic nucleus of the rat hypothalamus

We have previously shown that prolonged alcohol ingestion leads to neuronal loss in the supraoptic nucleus of the rat and that the surviving neurons, mainly the vasopressinergic ones, display marked increase in volume. In an attempt to establish correlates for the volumetric alterations we have studied the organelles of supraoptic nucleus neurons in three groups of rats--ethanol-fed, pair-fed, and dehydrated, in all cases treated from 2 to 12 months of age. The volume and surface area of the rough endoplasmic reticulum and Golgi apparatus, and the volume of nucleoli and neurosecretory granules were estimated on the basis of the respective volume and surface densities. The volumes and surface areas of all quantified organelles were increased in both alcohol-fed and dehydrated animals, although the increases were greater in the former group. Changes in the organelles studied are commonly regarded as reliable indicators of the neurosecretory activity of magnocellular neurons. Thus, our results suggest that under conditions of chronic alcohol exposure, the synthesizing activity of the surviving supra-optic neurons is augmented to compensate for the alcohol-induced neuronal loss and/or as a consequence of the alcohol-induced hyperosmolality. Changes in the transport and release of the neurosecretory material cannot, however, be ruled out as an additional cause of neuronal enlargement.