Brain levels and turnover rates of presumptive neurotransmitters as influenced by administration and withdrawal of ethanol in mice

High Ethanol and Acetaldehyde Inhibit Glutamatergic Transmission in the Hippocampus of Aldh2-Knockout and C57BL/6N Mice: an In Vivo and Ex Vivo Analysis

We aimed to investigate whether ethanol (EtOH) and acetaldehyde (AcH) can affect glutamate and its receptors GluN1 and GluA1 in the hippocampus of Aldh2-knockout (Aldh2-KO) and C57BL/6N (wild-type (WT)) mice. To do this, we first examined the effect of local administration of EtOH (100 mM, 200 mM, and 500 mM) and AcH (100 μM, 200 μM, and 500 μM) on extracellular glutamate levels in freely moving mice. Retrodialysis of 200 mM and 500 mM EtOH into the hippocampus of WT and Aldh2-KO mice produced significant decreases in extracellular glutamate levels (p < 0.05). A dose of 500 mM EtOH induced a greater decrease in Aldh2-KO mice (p < 0.05) than in WT mice, indicating the action of AcH. Similarly, perfusion of 200 μM and 500 μM AcH decreased glutamate in Aldh2-KO mice (p < 0.05), but this decrease was not seen in WT mice at any AcH dose. Second, we tested whether the EtOH- and AcH-induced decrease in glutamate was associated with decreases in GluN1 and GluA1 expression, as measured by real-time PCR and Western blot. We found a significant decrease in GluN1 (p < 0.05) and GluA1 (p < 0.05) subunits after a high dose of EtOH (4.0 g/kg) and AcH (200 mg/kg) in WT mice. However, a 2.0 g/kg dose of EtOH did not produce a consistent decrease in GluN1 or GluA1 between messenger RNA and protein. In Aldh2-KO mice, all three doses of EtOH (1.0 g/kg, 2.0 g/kg, and 4.0 g/kg) and AcH (50 mg/kg, 100 mg/kg, and 200 mg/kg) decreased GluN1 expression (p < 0.05), while moderate-to-high doses of EtOH (2.0 g/kg and 4.0 g/kg) and AcH (100 mg/kg and 200 mg/kg) decreased GluA1 expression (p < 0.05). Together, these in vivo and ex vivo data suggest that EtOH and AcH decrease extracellular glutamate in the hippocampus of mice with a concomitant decrease in GluN1 and GluA1 subunits, but these effects require relatively high concentrations and may, therefore, explain the consequences of EtOH intoxication.

Possible involvement of ACSS2 gene in alcoholism

Alcoholism is a psychiatric disorder that composes one of the principal causes of health disabilities in the world population. Furthermore, the available pharmacotherapy is limited. Therefore, this research was carried out to better understand the basis of the underlying neurobiological processes of this disorder and to discover potential therapeutic targets. Real-time PCR analysis was performed in the amygdala nuclei region of the brain of mice exposed to a chronic three-bottle free-choice model (water, 5 and 10% v/v ethanol). Based on individual ethanol intake, the mice were classified into three groups: "compulsive-like" (i.e., ethanol intake not affected by quinine adulteration), "ethanol-preferring" and "ethanol non-preferring". A fourth group had access only to tap water (control group). The candidate gene ACSS2 was genotyped in human alcoholics by real-time polymerase chain reaction using the markers rs6088638 and rs7266550. Seven genes were picked out (Acss2, Acss3, Acat1, Acsl1, Acaa2, Hadh, and Hadhb) and the mRNA level of the Acss2 gene was increased only in the "compulsive-like" group (p = 0.004). The allele frequency of rs6088638 for the gene ACSS2 was higher in the Alcoholic human group (p = 0.03), although sample size was very small. The gene ACSS2 is associated with alcoholism, suggesting that biochemical pathways where it participates may have a role in the biological mechanisms susceptible to the ethanol effects.

The effect of chronic ethanol consumption on muscarinic receptors in rat brain

Ethanol (15% v/v) was administered in the drinking water to male Wistar rats over period of 3 months. Binding properties of muscarinic receptors were studied in synaptosomes from selected brain areas using [(3)H]quinuclidinyl benzilate and its displacement by the selective antagonist, pirenzepine and the agonist, carbachol. Dissociation constants (K(d)) of all three ligands in the cerebral cortex, hippocampus and striatum of ethanol-treated groups did not differ from those in controls. Density of [(3)H]quinuclidinyl benzilate binding sites in the cortex of ethanol-treated animals was approx. 50% higher than in controls (2.06 +/- 0.2 and 1.32 +/- 0.2 pmol/mg of protein respectively, mean +/- SD, n = 6, P < 0.001). This was largely attributable to an increase in M(1) binding sites as shown by pirenzepine displacement studies. In the hippocampus and striatum binding capacity of muscarinic receptors was not affected by ethanol treatment. Synthesis of acetylcholine in cerebral cortex prisms from ethanol-treated animals was not inhibited under resting conditions, but stimulation of synthesis by high K(+) concentration was significantly altenuated by comparison with controls. These results suggest that chronic ethanol consumption induces changes in cholinergic neurotransmission in selected brain areas.

Effects of an aqueous extract of Puerariae flos (Thomsonide) on impairment of passive avoidance behavior in mice

The effects of an aqueous extract of Puerariae flos (Thomsonide) on ethanol-induced learning and memory impairment and scopolamine-induced amnesia were investigated. Thomsonide exerted an ameliorating effect on the impairment of both memory registration and memory retrieval induced by ethanol. These results indicate that Thomsonide has an antiamnesic effect on the central nervous system in alcoholic intoxication and support the traditional use of Puerariae flos for the treatment of alcoholic intoxication. Thomsonide also improved the scopolamine-induced impairment of memory registration in passive avoidance behavior in mice. The results of this study suggest that it may be possible to use Thomsonide for the treatment of age-related memory impairment and dementia.

The effects of chronic ethanol consumption and withdrawal on passive avoidance task and serum cholinesterase level in rats

The effects of chronic ethanol consumption and ethanol withdrawal on serum cholinesterase (ChE) activity and passive avoidance task in rats were investigated. Ethanol was administered to rats by a modified liquid diet with 4.8% (v/v) ethanol for 3 days followed by 25 days on a liquid diet in which the ethanol concentration was increased to 7.2%. Control rats were pair fed with an isocaloric liquid diet not containing ethanol. ChE activity and blood ethanol concentration were measured at the end of the 4.8% ethanol consumption and after 25 days of ethanol (7.2%) feeding and, just before and 24th and 72nd h of ethanol withdrawal period. Passive avoidance acquisition was evaluated for 150 s (cut-off time) in three individual groups of ethanol-administered, ethanol withdrawn (24th and 72nd h of withdrawal) and control rats. Locomotor activity of the rats was also measured and evaluated. The daily ethanol consumption of the rats ranged from 11.5 to 14.9 g/kg. ChE activities of the ethanol feeding rats were significantly increased as compared to control rats at the 3rd (4.8% ethanol) and 25th days of chronic ethanol (7.2%) consumption and 24th h of ethanol withdrawal. It returned to control values at the 72nd h of the withdrawal. Blood ethanol levels were measured as 200 and 2.2 mg/dl at just before ethanol withdrawal and 24th h of ethanol withdrawal, respectively. Both chronic ethanol consumption and late period of ethanol withdrawal produced some significant decreases in passive avoidance latency of the rats. Our results suggest that chronic ethanol consumption and late period of ethanol withdrawal may be related to impairment of passive avoidance task in rats. In addition, serum ChE levels do not seem to be involved in impairment of cognitive functions in ethanol dependent-rats.

Effect of exogenous melatonin on ethanol-induced changes in Na(+),K(+)- and Ca(2+)-ATPase activities in rat synaptosomes

In the present study, the effects of acute ethanol (EtOH) toxicity and of exogenous melatonin (MLT) on this toxicity were examined by measuring membrane-bound ATPases and acetylcholinesterase activities in rat synaptosomal membranes. The concentrations of plasma alpha-tocopherol and adrenal ascorbic acid (AA) were also measured. Synaptosomal Na(+),K(+)-ATPase and Ca(2+)-ATPase activities were significantly depressed in acute EtOH-intoxicated rats compared with controls, while acetylcholinesterase activity remained unaltered. Pretreatment with MLT (10 mg/kg) prior to acute EtOH administration prevented EtOH-induced inhibition of ATPases. Adrenal AA and plasma alpha-tocopherol levels were also depressed regardless of MLT pretreatment. MLT treatment alone affected neither membrane-bound enzyme activities nor tissue and blood levels of vitamins C and E. It is concluded that acute EtOH intoxication disturbs neural transport functions through the membrane-bound ATPase activity depression. Reduced AA and alpha-tocopherol levels may contribute to the neurodegenerative effects of EtOH. However, pretreatment with a high dose of MLT before EtOH administration may be beneficial to prevent EtOH-induced toxicity on ATPase-mediated neural transport functions.

Effects of MK-801 and ethanol combinations on memory consolidation in CD1 mice: involvement of GABAergic mechanisms

In the present research the effect of the noncompetitive N-methyl-d-aspartate receptor antagonist MK-801 and ethanol combinations on memory consolidation and the involvement of GABAergic mechanisms in this effect were investigated in CD1 mice injected intraperitoneally with the drugs immediately or 120 min after training in a one-trial inhibitory avoidance apparatus and tested for retention 24 h later. The results showed that (a) the retention performances of mice were impaired in a dose-dependent manner by immediate posttraining MK-801 (0.2 and 0.3, but not 0.1 mg/kg) and ethanol (1 and 2, but not 0.5 g/kg) administrations; (b) an otherwise ineffective dose of MK-801 (0.1 mg/kg) enhanced the deleterious effect exerted by ethanol (1 and 2 g/kg); (c) an otherwise ineffective dose of muscimol (0.5 mg/kg) enhanced, while otherwise ineffective doses of picrotoxin (0.25 mg/kg) or bicuculline (0.1 mg/kg) antagonized, this effect; and (d) no effect was observed when the treatments were carried out 120 min after training, suggesting that the effects observed following immediate posttraining administrations were due to the influence on the consolidation of memory. From these experiments it is evident that (a) MK-801 enhances ethanol's effects on memory consolidation and (b) GABAergic mechanisms are involved in this effect.

The contribution of mild thiamine deficiency and ethanol consumption to central cholinergic parameter dysfunction and rats' open-field performance impairment

We studied at the biochemical, morphological, and behavioral levels the effect of chronic ethanol consumption, associated or not with a mild thiamine deficiency episode. We found that (i) thiamine deficiency induced a significant decrease of the acetylcholinesterase (AChE) activity both in cortex and hippocampus; (ii) chronic ethanol treatment has no effect on cortical AChE activity, but induced a significant decrease of hippocampal enzyme activity; (iii) the reduction in cortical and hippocampal AChE activity induced by chronic ethanol treatment associated with a 1-week thiamine deficiency was also significant and was greater than that induced by ethanol alone. Furthermore, either chronic ethanol or thiamine deficiency induced a significant decrease in the release of acetylcholine (ACh) in the stimulated condition using high potassium concentration; and when both treatments were associated the decrease was even greater. In the unstimulated condition, the reduction in the release of ACh was greater for ethanol treatment than for thiamine deficiency. Open-field tests showed that only in the "sniffing" category were there significant differences among the experimental groups. No morphological change was detected by optical microscopy, suggesting that the injury process was in its initial stages in which only functional and behavioral changes are displayed. In addition, our biochemical results indicate that cortical cholinergic susceptibilities to ethanol and thiamine deficiency are significantly different.

Influence of acute and chronic ethanol treatment on muscarinic responses and receptor expression in Chinese hamster ovary cells

The influence of ethanol on the muscarinic receptor-mediated release of inositol phosphate from Chinese hamster ovary (CHO) cells stably transfected with one of the five subtypes of muscarinic acetylcholine receptor was determined. In CHO cells expressing M3 muscarinic receptors (CHO-M3), carbamylcholine increased muscarinic receptor-induced release of inositol phosphate by 150-350% following a 15-min incubation with an EC50 of approximately 30 microM. Maximal responses were obtained with 1 mM carbamylcholine, while responses to 10 mM carbamylcholine were somewhat less than maximal. Preincubation with atropine for 10 min inhibited the response with an IC50 of approximately 30 nM. CHO cells transfected with M1, M3, and M5 receptors displayed a similar pattern of activity; CHO cells transfected with M2 and M4, as well as untransfected cells, were unresponsive to carbamylcholine. Ethanol acutely inhibited the response of CHO-M3 cells to carbamylcholine by 15% at 18 mM and by 47% at 180 mM (the highest concentration examined). CHO-M3 cells were incubated with 50 mM ethanol for 48 hr. This treatment did not affect the number of cells or their protein content (113 pg/cell). The expression of M3 muscarinic receptors (determined using [3H]N-methylscopolamine) increased from 1.34 +/- 0.23 to 1.75 +/- 0.16 pmol/mg protein (P < 0.05). In contrast, carbamylcholine-stimulated release of inositol phosphate was depressed by 40-70% in four experiments. Concentration-response analyses indicated a non-competitive inhibitory mechanism. This dissociation of muscarinic receptor expression and muscarinic signaling suggests a compensatory increase in receptor expression in response to chronic inhibition of muscarinic signaling by ethanol.

Reduction of regional brain glucose metabolism following different durations of chronic ethanol consumption in mice: a selective effect on diencephalic structures

The effects of chronic alcohol consumption on regional brain glucose metabolism were examined in Balb/c mice using the [14C]2-deoxyglucose autoradiographic technique. Animals were given a solution of 12% v/v ethanol as their only source of fluid for either 6, 12 or 18 months and compared to control groups receiving either an isocaloric solution or saccharose or tap water. Alterations of cerebral brain glucose metabolism were assessed in mice who were returned to a non-alcoholic diet and allowed to freely explore a T-maze. The results showed that chronic ethanol consumption induced reductions of regional metabolic activity which were functions both of the duration of alcohol treatment and of the structure studied. Whereas a six month period of alcoholization did not induce any significant effects on metabolic activity, 12 months of treatment were necessary to induce the first observable and significant reductions in [14C]2-deoxyglucose labelling. These effects were mainly limited to diencephalic structures such as the lateral mammillary nuclei and the anterodorsal thalamic nuclei. The cerebellum was also affected but to a lesser degree. After 18 months of alcoholization, a generalized spread of the metabolic reduction to the entire mammillary complex (lateral, medial and posterior nuclei) and to the thalamic nuclei was observed. This same duration of treatment was necessary to induce the first detectable decrease of metabolic activity in the hippocampus. In agreement with data from human neuropathology, these findings confirm the particular vulnerability of diencephalic structures to ethanol and suggest that damage limited to diencephalic regions rather than to hippocampal or cortical areas could be primarily responsible for the memory disorders observed in Korsakoff's syndrome.

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.

GABA-transaminase in brain and blood platelets: basic and clinical aspects

Several lines of evidence suggest that the major inhibitory neuro-transmitter, gamma-aminobutyric acid (GABA) is involved, both directly and indirectly, in the pathogenesis of certain neurological and psychiatric disorders. The main enzyme responsible for GABA catabolism is gamma-aminobutyrate aminotransferase (GABA-T). Inhibition of this enzyme produces a considerable elevation of brain GABA concentrations, and such elevation has been correlated with many pharmacological effects. There seems to be that, as is discussed below, GABA-T activity in the brain and/or blood platelets is related to some neuro-psychiatric disorders such as alcoholism, epilepsy and Alzheimer's disease. GABA-T has been identified in the blood platelets with similar characteristics to those of brain GABA-T. In this way, studies on GABA-T activity in neuro-psychiatric disorders could be performed to understand, diagnosis and treat GABA-related disorders of the central nervous system (CNS).

Serotonin and alcohol intake, abuse, and dependence: findings of animal studies

Despite a relatively large body of literature on the role of the neurotransmitter serotonin (5-hydroxytryptamine, or 5-HT) in the regulation of alcohol intake, the functional significance of serotonergic neurotransmission and its relationship to alcohol intake, abuse, and dependence remains to be fully elucidated. In part two of this review, the experimental (animal) data is summarized along two lines: the effects of serotonergic manipulations on the intake of alcohol, and the effects of acute and chronic alcohol intake, as well as the withdrawal of chronic alcohol, on the serotonergic system. It is concluded that serotonin mediates ethanol intake as a part of its larger role in behavior modulation, such that increases in serotonergic functioning decrease ethanol intake, and decreased serotonergic functioning increases ethanol intake. Ethanol produces transient increases in serotonergic functioning that activate the mesolimbic dopaminergic reward system. The results are discussed in light of recent theories describing the regulatory role of serotonin in general behavior.

Increase in brain GABA-transaminase activity after chronic ethanol treatment in rats

The activity of gamma-aminobutyrate aminotransferase (GABA-T) was measured in the brains of rats treated both acutely and sub-chronically with ethanol. Previously, chronic treatment with ethanol for 90 weeks was found to increase the mean brain GABA-T activity by 20-45%. In the present study acute ethanol treatment (4 g/kg, i.p.) did not induce and change in the activity of brain GABA-T with the exception of a small increase in the cerebellum (8%) and, after repeated treatment with ethanol (4 g/kg/day, i.p.) for one and two weeks, no change in the activity of GABA-T was also found in any of the brain regions examined. Subchronic treatment with ethanol for 14 weeks, performed according to two different schedules involving a voluntary intake of ethanol in the drinking water, resulted in approximately a two-fold difference in ethanol intake. A mean increase of 50-85% in the activity of GABA-T was found in all the brain regions of rats with higher ethanol intake in comparison with the group of rats with lower ethanol intake. A bimodal distribution of brain GABA-T activity, however, was found in the ethanol-treated rats, with 60% of the rats having a two-fold increase and the remaining 40% having unchanged activities. The addition of pyridoxal phosphate to the incubation media increased the activity of brain mitochondria from ethanol-treated rats with high brain GABA-T, whereas there was a decrease in the activity in control rats and in ethanol-treated rats in which no increase in brain GABA-T had occurred. These results show firstly, that in a subpopulation of rats, subchronically treated with ethanol for 14 weeks, there was a two-fold increase in brain GABA-T activity, while in another subgroup no change occurred, and, secondly, that this increase in GABA-T activity was a consequence of a change in the response of the apoprotein to the addition of the cofactor pyridoxal phosphate.

Brain GABA-transaminase and monoamine oxidase after chronic ethanol treatment in rats

The activities of gamma-aminobutyrate aminotransferase (GABA-T) and monoamine oxidase (MAO-A and -B) were estimated in various brain regions of rats exposed to ethanol for 90 weeks. During the first period (weeks 1-58), the rats had access to both ethanol (10% w/v) and water during a 24-hr interval at the end of each week. At this point, the animals were given either a saline injection (intraperitoneally, group 1) or an ethanol injection (2.0 g/kg ip, group 2). During the second period (weeks 59-90), the rats in groups 1 and 2 had continuous access to both ethanol and water. The third group was composed of untreated control rats. Compared with controls, there was an increase of 20-45% in the mean brain GABA-T activity in both groups of ethanol-treated rats. However, analysis of the data for the individual ethanol-treated rats revealed a considerable difference in brain GABA-T activity. Thus, approximately 30% of the ethanol-treated rats showed approximately twice the activity of rats in the exposed groups and in the control group. There was no connection between ethanol intake, water intake, or body weight and GABA-T activity in any of the brain regions examined. There was no effect of ethanol in vitro on the activity of GABA-T in the brain cortex in concentrations of 20-100 mM, whereas acetaldehyde inhibited the activity by 15% at these concentrations. The present results suggest that there is a bimodal distribution with respect to the effect of ethanol on rat brain GABA-T activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Ethanol differentially affects extracellular monoamines and GABA in the nucleus accumbens

The magnitude, direction, and time course of the effects of acute administration of ethanol (0.1 or 1.0 g/kg) on the extracellular levels of dopamine (DA), dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), 5-hydroxytryptamine (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), and GABA within the nucleus accumbens of the rat were analysed using microdialysis in conjunction with high-pressure liquid chromatography and electrochemical detection. IP injection of 0.1 g/kg ethanol failed to modify the extracellular concentration of DA, DOPAC, HVA, 5-HT, 5-HIAA, and GABA in the nucleus accumbens during the 120-min collection period. On the contrary, 1.0 g/kg IP ethanol significantly increased extracellular levels of DA, DOPAC, and 5-HIAA in microdialysates from the nucleus accumbens. The maximal increase in DA (314.87 +/- 6%), DOPAC (210.58 +/- 3%), and 5-HIAA (250.88 +/- 8%) was observed 40 min after administration of ethanol. Extracellular HVA was also enhanced (220.89 +/- 2%) at time point 100 min following injection of the same dose of ethanol. Finally, extracellular levels of 5-HT and GABA remained unchanged following 1.0 g/kg ethanol.

Long-term ethanol consumption by rats: effect on acetylcholine release in vivo, choline acetyltransferase activity, and behavior

The extent and duration of cholinergic hypofunction induced by long-term ethanol consumption was investigated in the rat. Ethanol (20% v/v) was administered to male adult Wistar rats as a sole source of fluid for three or six months. Control rats received tap water. The body weight, food and fluid intake in ethanol-treated rats were lower than in control rats throughout the treatment. After three months of ethanol consumption, and one week withdrawal, acetylcholine release in freely moving rats, investigated by microdialysis technique coupled to high-performance liquid chromatography quantification, was significantly decreased by 57 and 32% in the hippocampus and cortex, respectively, while choline acetyltransferase activity was significantly decreased (-30%) only in the hippocampus. A complete recovery of choline acetyltransferase activity and acetylcholine release was found after four ethanol-free weeks. Conversely, after four weeks of withdrawal following six months of ethanol treatment, the recovery in acetylcholine release was not accompanied by that in choline acetyltransferase activity, which remained significantly lower than in control rats in both cortex and hippocampus. The ability of rats to negotiate active and passive avoidance conditioned response tasks, tested after four ethanol-free weeks, was strongly impaired in both three- and six-month ethanol-treated rats. In conclusion, our experiments demonstrate that the development of a long-lasting cholinergic hypofunction requires at least six months of ethanol administration. The hypofunction affects choline acetyltransferase activity and acetylcholine release differently, and undergoes a remarkable recovery.

Hippocampal cholinergic alterations and related behavioral deficits after early exposure to ethanol

The present study was designed to ascertain septohippocampal cholinergic alterations and their related behavioral deficits after early exposure to ethanol. Mouse pups were exposed to ethanol, 3 g/kg by daily subcutaneous injection on postnatal days 2-14. At age 50 days, the ethanol-exposed mice had significant reductions from control levels in eight-arm maze performance. For example, on the fourth testing day, the number of correct entries in the ethanol group was 21% below control levels (P < 0.05) and the number of trials needed to enter all arms was 48% above control (P < 0.001). It took the ethanol-exposed mice twice the time to reach criterion than it did control (P < 0.01). A 33% increase from control level in muscarinic receptor number (Bmax) was found in the treated mice of age 22 days and a 64% increase at age 50 days (P < 0.001). However, no differences between control and treated groups could be detected in the presynaptic component of the cholinergic innervation, choline acetyltransferase activity. The results suggest that early ethanol exposure acts on hippocampal function similarly to phenobarbital, probably via alterations in postsynaptic processes in the septohippocampal cholinergic pathways.

Platelet serotonin levels in alcoholic patients: changes related to physiological and pathological factors

This study investigated platelet serotonin (5-hydroxytryptamine; 5-HT) levels and the effects of different physiological and pathological factors in 108 alcoholic patients (alcohol abuse, n = 49; alcohol dependence, n = 59) and 32 healthy control subjects. Platelet 5-HT levels were determined by a fluorescent-ortho-phthalaldehyde assay. In patients, platelet 5-HT levels during withdrawal from alcohol and after 2 weeks of abstinence were significantly lower than in control subjects. Among patients, this decrease was enhanced both in alcohol-dependent patients and in patients who were depressed during the withdrawal phase, whereas lifetime impulse control disorders (mostly found in alcohol abusers) were associated with comparatively high platelet 5-HT levels (i.e., close to control subjects' values). These results, which reflect the likely biphasic effect of alcohol ingestion upon 5-HT functioning, are consistent with the dimensional 5-HT hypothesis in psychiatric disorders.

Cholinergic mechanisms in physical dependence on barbiturates, ethanol and benzodiazepines

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

Alcohol, head injury, and neuropsychological function

Evidence is reviewed indicating that the extent of alcohol abuse alone cannot account for the neuropsychological deficits observed in alcoholics, and that alcohol abuse and head injury may interact in some patients to influence neuropsychological status. Alcohol abuse both increases the risk for head trauma and potentiates the resulting brain injury, which can lead to negative neuropsychological consequences. Clinicians involved in the treatment of addiction should assess patients for history of head injury, and neuropsychological deficits consequent to both head injury and ethanol. These deficits may limit patient ability to comply with addiction rehabilitation programs. Conversely, clinicians in acute care and rehabilitation of the sequelae of head trauma should routinely assess their patients for substance abuse, because such abuse can have a significant impact on recovery from brain injury.

Acamprosate modulates synaptosomal GABA transmission in chronically alcoholised rats

Male Sprague-Dawley rats were pulmonary alcoholised for 30 days. Six were treated with acamprosate (400 mg/kg/day, PO) during alcoholisation. The control nonalcoholised group also received acamprosate (400 mg/kg/day, PO) during the 30 days. At the end of the experiment, brains areas (cortex, hippocampus, thalamus, striatum, and olfactory bulbs) were dissected for the study of synaptosomal 3H-GABA uptake. In another experiment, GABA levels were determined in the same areas using HPLC with electrochemical detection. Blood ethanol levels were also measured during alcoholisation. Acamprosate treatment did not modify blood ethanol levels. In cortex and olfactory bulbs, alcoholisation increased 3H-GABA uptake (Vmax) with an increase in the affinity (Km). 3H-GABA uptake was not affected by alcoholisation in other brain areas. In hippocampus and thalamus, acamprosate treatment enhanced 3H-GABA uptake (Vmax) only in alcoholised rats. Moreover, in thalamus, alcoholisation enhanced GABA levels. The effect of alcohol and acamprosate on GABA presynaptic events is discussed and it is concluded that the action of ethanol and acamprosate on GABA transport could be, in part, responsible for the modulation by acamprosate treatment of ethanol behaviour.

Recent Advances in Pharmacological Research on Alcohol

Alcohol dependence is a major public health problem. Studies have shown that a person dependent on alcohol often coabuses other substances, such as cocaine. Cocaine is a powerful stimulant whereas ethanol is generally considered to be a depressant, with some stimulating properties. The subjective effects of these two substances in a dependent individual may often appear to be more similar than they are different. Animals also self-administer both substances. Basically, although both substances have anesthetic properties and both act to functionally increase catecholaminergic function, especially that of dopamine, there are some differences in their actions. Both alcohol and cocaine have various effects on several neurotransmitters and systems, which ultimately interact to produce the feeling of well-being avidly sought by many individuals today. This drive often eventually produces a dependence which has associated social and medical consequences. It seems likely that the neurochemical changes that ensue following abuse of these substances underlie the phenomena of dependence, tolerance, and subsequent withdrawal. The apparent similarities and differences between these two substances will be reviewed in this chapter.

Neuropharmacology of Cocaine and Ethanol Dependence

Drug addiction includes two important characteristics, chronic compulsive or uncontrollable drug use and a withdrawal syndrome when use of the drug is stopped. Animal models for the motivational components of drug dependence have been developed allowing a systematic exploration of the neurobiological mechanisms of drug dependence. The reinforcing actions of acute cocaine as measured by intravenous cocaine self-administration appear to be mediated by the presynaptic release of dopamine in the region of the nucleus accumbens and may preferentially involve the dopamine D-1 receptor subtype. The nucleus accumbens circuitry involved in the reinforcing actions of cocaine may include the ventral pallidum and may be modulated by serotonin. Chronic cocaine produces increases in brain reward thresholds that may reflect the "dysphoria" and anhedonia associated with cocaine dependence and suggests a dysregulation of brain reward systems possibly involving dopamine. Reliable measures for the acute reinforcing effects of ethanol in nondependent animals have been established in the rat using a lever press operant and a taste habituation procedure. Important roles have been established for serotonin, GABA, dopamine, and opioids in the acute reinforcing properties of ethanol, perhaps acting on some of the same neural circuitry subsuming the reinforcing actions of other drugs of abuse. Studies of the motivational aspects of ethanol dependence have suggested a functional role for brain corticotropin-releasing factor. These results suggest that the neurobiology of drug dependence involves not only neurotransmitters that mediate the acute reinforcing properties of drugs, but also the aversive motivational and emotional aspects of drug withdrawal. Advances in our understanding of brain changes associated with the switch from acute effects to chronic actions may provide a key to our understanding of not only drug dependence, but also psychopathology such as, anxiety, and affective disorders.

Effects of age and alcoholism on the prevalence of panic disorder

Findings are reported evaluating the effects of aging and alcoholism histories on the 6-month prevalence rates of panic disorder. The data were collected in 5 communities as part of the Epidemiologic Catchment Area (ECA) study: New Haven, CT; Baltimore, MD; St. Louis, MO; Durham, NC; and Los Angeles, CA. Reanalysis of ECA data provided additional support for a decline in the prevalence of panic disorder among elderly people. In addition, the presence of a history of alcohol abuse or dependence was associated with significantly elevated panic disorder rates in younger individuals, but an earlier decline in panic disorder prevalence with age, regardless of gender. These findings offer preliminary support for neurodevelopmental hypotheses for the onset and outgrowing of panic disorder. They also highlight the impact of alcoholism on the course of panic disorder.

Endogenous opioids modulate the oxytocin response to insulin-induced hypoglycaemia and partially mediate the inhibitory effect of ethanol in man

Abstract The possible inhibition exerted by ethanol on the oxytocin (OT) response to insulin-induced hypoglycaemia was tested in man. Furthermore, the possibilities that endogenous opioids play a role in the control of hypoglycaemia and/or ethanol action on OT were examined. Insulin tolerance tests were performed in three groups of eight age- and weight-matched normal men treated with: 1) naloxone, group 1 1 mg bolus naloxone + 2.5 mg over 105 min, group 2 2 mg bolus naloxone + 5 mg over 105 min, group 3 4 mg bolus naloxone + 10 mg over 105 min; 2) ethanol (50 ml in 110ml of whiskey) to all the groups; 3) a combination of ethanol + naloxone; 4) normal saline. Furthermore, the effect of ethanol + naloxone (4+10mg) in the absence of insulin-induced hypoglycaemia was evaluated in seven additional subjects. During this latter test, the plasma levels of OT remained unchanged. Insulin-induced hypoglycaemia produced a 2.2-fold increment in plasma OT levels in the control experiments. This response was not changed by the treatment with the lowest dose of naloxone (1+2.5mg) in group 1, but it was significantly enhanced by administration of naloxone at higher doses (mean peak OT levels rose 2.8-fold in both group 2 and group 3). In all subjects the OT response to hypoglycaemia was completely abolished by ethanol. However, when ethanol was given together with naloxone, the hypoglycaemia-induced OT rise was only partially inhibited by ethanol. At all doses naloxone produced similar effects; in fact, in all groups OT rose 1.5-fold in response to hypoglycaemia during insulin tolerance test + ethanol + naloxone. Neither naloxone nor ethanol altered the basal secretion of OT, as tested during 45 min before the insulin tolerance test. These data demonstrate that the OT response to insulin-induced hypoglycaemia is inhibited by ethanol. Furthermore, the data indicate that endogenous opioids are involved in the control of hypoglycaemia-stimulated OT secretion and partially modulate ethanol inhibitory action.

Involvement of the cholinergic neuronal system and benzodiazepine receptors in alcohol-induced amnesia

We investigated the involvement of the GABAergic and cholinergic neuronal systems and benzodiazepine (BZP) receptors in ethanol-induced amnesia using a passive avoidance task. Pretraining administration of ethanol impaired the passive avoidance response. The BZP agonist chlordiazepoxide potentiated the amnesia, while the GABA antagonists bicuculline and picrotoxin failed to affect it. The acetylcholine esterase inhibitor physostigmine partially attenuated the ethanol-induced amnesia. These results suggest that ethanol-induced amnesia is related to BZP receptors and a dysfunction of the cholinergic neuronal system.

Serum prolactin increase induced by ethanol--a dose-dependent effect not related to stress

The effect of moderate ethanol doses (0.5 and 1 g/kg body weight) on serum prolactin (PRL), cortisol, epinephrine and norepinephrine concentrations was measured in a double-blind, placebo-controlled study. Eight healthy male volunteers participated. Blood was with drawn twice before, and 30 min, 60 min, 90 min and 120 min after oral ethanol intake. The higher ethanol dose, but not the lower dose, significantly increased PRL concentrations. Concentrations of cortisol, epinephrine and norepinephrine were not changed by either dose. Thus, the effect of ethanol on PRL appears to be dose-dependent and not stress-related.

A comparison of sensitivity to oxotremorine and muscarinic receptors in LS and SS mice

Several studies have suggested that ethanol interacts with muscarinic cholinergic systems in the brain. In order to assess whether muscarinic systems regulate sensitivity to ethanol, the effects of oxotremorine pretreatment on sensitivity to ethanol were determined in the long-sleep (LS) and short-sleep (SS) mice, which were selectively bred for differential sensitivity to ethanol. In addition, the relative sensitivity of these two lines to intraperitoneally (ip) injected oxotremorine and total muscarinic receptors, as measured by quinuclidinyl benzilate (QNB) binding, M1 receptor subtypes, as measured by pirenzepine (PZ) binding, and ratios of high and low agonist affinity were measured in seven brain regions. SS mice were more sensitive to oxotremorine-induced increases in sensitivity to ethanol but the LS mice were more sensitive to the effects elicited by ip oxotremorine injection. Because the effects of oxotremorine were blocked by scopolamine but not by methylscopolamine, it is likely that the effects of oxotremorine that were measured are centrally mediated. QNB binding did not differ between the LS and SS mice except for cortex where the SS mice exhibited slightly larger numbers. The mouse lines did not differ in the number of M1 receptors or in ratio of high to low affinity agonist sites. Therefore, it does not seem likely that differences in receptor numbers are important in regulating the differential sensitivities of the LS and SS mice to oxotremorine or ethanol. Differences in receptor coupling processes may be critically involved.

Platelet serotonin decrease in alcoholic patients

This study investigated the platelet 5-HT levels and their changes according to different physiological and pathological factors in 30 young alcoholic patients (16 alcohol abusers and 14 alcohol-dependent subjects) and 26 healthy controls. Platelet 5-HT levels were determined by a fluorescent-ortho-phthalaldehyde assay. The mean platelet 5-HT levels obtained in patients during withdrawal and after 2 weeks of abstinence were significantly lower than in controls. Presence of positive history of impulse control disorders (ICD) influenced the mean platelet 5-HT levels in patients. These preliminary results suggest that the platelet 5-HT level decrease observed in alcohol-dependent patients mostly free from ICD and in alcohol abusers mostly affected by ICD might result from comparable neurobiological mechanisms. However, the age of onset of alcohol dependence might depend on psychological functioning features.

Cholinergic system and memory in the rat: effects of chronic ethanol, embryonic basal forebrain brain transplants and excitotoxic lesions of cholinergic basal forebrain projection system

Oral administration of ethanol (20% v/v) to male Sprague-Dawley rats for different periods of time up to 28 weeks resulted in profound reductions of acetylcholine content, in vitro synthesis and release of acetylcholine, choline uptake, activities of choline acetyltransferase, acetylcholinesterase and pyruvate decarboxylase, content of noradrenaline, serotonin and, to a lesser extent, dopamine throughout the brain. Changes were fully and partially reversible by a 4 weeks' ethanol-free period following a treatment of 8 and 18 weeks, respectively. They remained persistent, however, after 28 weeks of treatment. Performance in an eight arm-radial maze revealed a severe impairment in both spatial and non-spatial reference and working memory. A similar pattern of memory impairment was obtained after ibotenate lesion of the cholinergic basal forebrain projection system. In order to test whether this memory impairment depends on cholinergic deafferentation of the cortex, cholinergic-rich fetal basal forebrain cell suspensions were transplanted into cortex, hippocampus or both these sites in ethanol treated rats. Cholinergic-rich transplants, but not cholinergic-poor transplants, were effective in ameliorating impaired memory function and measures of cholinergic activity in the basal forebrain projection system. The behavioural efficacy of the basal forebrain grafts was well correlated with measures of both transplant volume and the degree to which they restored acetylcholine content at the transplant site; these transplants had no effect, however, on brain monoamine levels. The effects of the cholinergic-rich transplants into cortical and hippocampal sites were additive in their amelioration of performance in the radial maze. Similarly, ibotenate lesions of the sites of origin of the cholinergic projections to neocortex (in the region of the nucleus basalis magnocellularis) and hippocampus (the medial septal areas and nucleus of the diagonal band), respectively, were additive in their deleterious effects on maze performance. There were no qualitative differences in the susceptibility of the four different types of memory performance measured (spatial and non-spatial reference and working memory) to the effects of ethanol, ibotenate lesions of the cholinergic projection system, or cholinergic-rich brain tissue transplants. Thus, overall, the results indicate that the forebrain cholinergic system acts as a whole, without major functional differences between the projections originating in the medial septal area/diagonal band complex and the basal nucleus, and that it discharges a very general function in cognitive processes.(ABSTRACT TRUNCATED AT 400 WORDS)

Loss of neurons in the rat basal forebrain cholinergic projection system after prolonged intake of ethanol

A reduction in the number of acetylcholinesterase (AChE)-positive neurons in the basal nucleus of Meynert complex (NbM, Ch 1 to Ch4) to 83% of control values was observed in rat after ethanol intake (20% v/v) for 12 weeks. Activity of choline acetyltransferase (ChAT) and AChE in the basal forebrain was simultaneously reduced to 74% and 81% and content of acetylcholine (ACh) to 56% of control values respectively. Neuronal loss showed a gradient over the rostro-caudal extension of the cholinergic projection system being most pronounced in the septal-diagonal band area and reaching 27% in the medial septum (Ch1). Number of AChE-positive neurons was insignificantly reduced in the pedunculopontine nucleus (Ch5) and unchanged in the laterodorsal tegmental gray of the periventricular area (Ch6). ACh content and activity of AChE was significantly reduced in target areas of the NbM such as cortex, hippocampus and amygdala, but changes were less pronounced than in the basal nucleus. The results indicate a neurotoxic effect of prolonged intake of ethanol on cholinergic neurons in the NbM leading to a partial cholinergic denervation of cortex, hippocampus and amygdala. Chronic intake of ethanol in rat is suggested to represent an animal model suitable to test the cholinergic hypothesis of geriatric memory dysfunction and to develop strategies for an amelioration of the impairment in memory and cognitive function in dementing disorders associated with a degeneration in the NbM such as postalcoholic dementia and Alzheimer's disease.

Effects of ethanol and pantothenic acid on brain acetylcholine synthesis

1. Measurements of brain acetylcholine (ACh) synthesis from precursor [14C]-pyruvate, pantothenic acid (PA) concentration in the brain, and blood ethanol (EtOH) concentration were made in rats treated with either ethanol (5-6 g kg-1 body wt daily) alone or ethanol with PA supplementation (100-200 mg kg-1 body wt daily). EtOH with or without PA was administered orally by either Lieber-Decarli liquid diet for 4 weeks and 4 months or by oral intubation for 1 and 4 days. Matched controls were given either ethanol-free liquid diet or saline. 2. ACh synthesis in the brain of rats treated with ethanol alone for 4 months was significantly (P less than 0.01) inhibited. PA concentration of the brain was diminished to 7.0% of the control value. 3. PA concentration in the brain of rats treated with ethanol plus PA for 4 months was three times that of rats treated with ethanol alone. ACh synthesis in rats with ethanol and PA supplementation was also significantly (P less than 0.01) higher. 4. There was no difference in blood EtOH concentration between rats treated with ethanol with or without PA supplement. 5. The EtOH effect on ACh synthesis and PA concentration in the brain was observed in the chronic treatments but not in the acute treatments. 6. Data suggest that chronic ethanol exposure may decrease ACh synthesis by depleting PA, a precursor for the synthesis of acetyl CoA. Acetyl CoA is an essential substrate for ACh synthesis.

Ethanol inhibition of synaptosomal high-affinity choline uptake

Ethanol in vitro inhibited synaptosomal sodium-dependent, high-affinity choline uptake, the rate-limiting step in the synthesis of acetylcholine. This inhibition occurred with ethanol concentrations as low as 50 mM, was reversible and was not attributable to ethanol effects on synaptosomal membrane potential. In contrast, ethanol concentrations as high as 400 mM had no effect on synaptosomal high-affinity uptake of gamma-aminobutyric acid, a major inhibitory neurotransmitter in the central nervous system. The observed ethanol inhibition of choline uptake is consistent with suggestions that depression of cholinergic systems is important in acute ethanol intoxication.

Effects of ethanol on passive avoidance behavior in the mouse: involvement of GABAergic mechanisms

A passive avoidance methodology was used to test the effect of ethanol, and its interference with GABAergic mechanisms, on memory in male CD1 mice. Retention performance was reduced in a dose-related manner, by ethanol and by muscimol, a GABA agonist, while it was increased by the GABA antagonists picrotoxin and bicuculline. These effects were evident when treatments were carried out immediately, but not 120 min, after training, suggesting that they were due to a specific action of the drugs on the time-dependent memory consolidation process. The ethanol-induced reduction of retention performance was enhanced by muscimol and decreased by picrotoxin and bicuculline administrations. Taken together the results confirm the involvement of a GABAergic mechanism in memory consolidation and demonstrate that it underlies the negative effect of ethanol on passive avoidance behavior in the mouse.

Alterations of fetal brain biogenic amine metabolites by maternal ethanol exposure

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

Castration and tolerance induces changes in the levels of the activity of acetylcholinesterase in the isolated vas deferens of the rat

Changes in the activity of acetylcholinesterase (AChE) of the isolated vas deferens from normal, castrated, morphine and ethanol-tolerant rats were studied. Three days after the termination of treatment with morphine and on the last day of treatment with ethanol, a significant inhibition of the activity of AChE was detected. This reduction in the enzymatic activity persisted in morphine-tolerant rats for 15 days, but not for 30 days, at which time the levels of AChE were determined to be normal. However, in ethanol-tolerant rats, there were no significant changes found at days 15 or 30. The activity of AChE was decreased significantly in castrated rats, but this effect was reversed by treatment with testosterone. During withdrawal from morphine or ethanol, the levels of AChE were significantly increased. The results indicate that morphine and ethanol may be inducing changes in the feedback mechanism which regulates the levels of AChE at post-synaptic sites, and these changes could play an important role in the development of tolerance to morphine and to ethanol.

A systematic regional study of brain salsolinol levels during and immediately following chronic ethanol ingestion in rats

Regional contents of salsolinol and catecholamines in the brain of normal and ethanol-treated rats were studied. Male Sprague Dawley rats were given ethanol solution as sole drinking fluid for 3, 4, 5 or 6 months. Salsolinol determined by gas chromatography mass spectrometry was found to be present in the hypothalamus and the striatum of control rats. The levels of salsolinol in these regions increased significantly by long-term ethanol drinking and rapidly decreased to control levels following its removal. Salsolinol levels in other regions of rat brain were extremely low or negative and unaltered upon chronic ethanol treatment. In ethanol-treated rats the hypothalamic salsolinol, although generally higher than in the striatum, increased along with the ethanol exposure, whereas the striatal salsolinol was constant during those periods of study. Brain dopamine (DA) and norepinephrine contents remained unaltered during and immediately after chronic ethanol treatments. No correlation of salsolinol levels with DA contents or blood ethanol concentrations was observed. The occurrence of salsolinol in selected areas of rat brain with lack of changes in catecholamine level but as a result of an in vivo formation by long-term ethanol drinking was considered to be due to an alteration of acetaldehyde metabolism in the liver and brain.

Effect of combined exposure to lead and ethanol on some biochemical indices in the rat

We investigated the effect of daily oral administration to young rats of lead (10 mg/kg) and ethanol (10%, v/v, in drinking water), either alone or in combination, for 8 weeks on the uptake of lead in tissues, brain biogenic amines, hepatic alcohol dehydrogenase and cytosolic and mitochondrial aldehyde dehydrogenase and some selected lead-sensitive variables. Lead given in combination with ethanol produced more pronounced inhibition in the activities of hepatic glutamic oxalacetic transaminase (GOT) and glutamic pyruvic transaminase (GPT) as compared to lead alone treatment. Simultaneous exposure to lead and ethanol produced a greater depression of dopamine (DA) and 5-hydroxytryptamine (5-HT) levels in the whole brain of rats, compared to rats treated with lead alone. The concentrations of lead in blood, liver and brain were significantly higher in rats exposed simultaneously to lead and ethanol. Though ethanol treatment alone inhibited the activities of hepatic alcohol dehydrogenase and cytosolic and mitochondrial aldehyde dehydrogenase, no effect of lead treatment alone on these variables was observed. The results suggested that animals exposed to ethanol and lead are more vulnerable to the neurologic and hepatotoxic effects and the systemic toxicity of lead.

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.

Central cholinergic correlates of low dose ethanol-induced locomotor stimulation

Brain area levels of acetycholine and choline plus the turnover rate of acetylcholine were measured in three strains of rats given low, locomotor-stimulating doses of ethanol. Maudsley reactive (MR/N), Sprague-Dawley, and randomly bred MR/N (MRrb) rats were killed by microwave irradiation and cholinergic function was measured by gas chromatography/mass spectroscopy methods. The results show that the MR/N strain (2 and 5 months old), which elicits enhanced locomotor stimulation after low doses of ethanol, also demonstrates significant increases in cholinergic function at the time of behavioral stimulation. However, after locomotor stimulation, cholinergic parameters returned to normal in these animals. Strains which do not show enhanced locomotor activity after ethanol did not demonstrate significant central cholinergic changes. We conclude that central cholinergic function is related to behavioral stimulation elicited by low doses of ethanol in the MR/N rat strain but not other strains.

Effect of ethanol on erythrocyte acetylcholinesterase activity

Erythrocyte acetylcholinesterase (AchE) activity was measured in the blood of 36 alcoholic subjects and 41 healthy volunteers. The mean activity in the alcoholics was significantly lower than that in the control subjects. In vitro experiments showed that ethanol inhibited the AchE activity immediately and in proportion to the concentration of ethanol used. Incubation times up to 6 h did not increase the inhibition significantly. Incubation of normal red cells with ethanol for 15 h, followed by washing, showed also that AchE activity was inhibited by the previous exposure to ethanol and that washing did not reduce the inhibitory effect. The possibility is considered that depressed erythrocyte AchE activity may be an early indication of potential disturbances of the autonomic nervous system. The importance of reporting ethanol intake in patients with organophosphorus poisoning is stressed.

Effect of ethanol on the binding of 35S-T-butylbicyclophosphorothionate to mouse brain membranes

The effect of in vitro addition of ethanol (0.02-1.0 M) on the binding of 35S-TBPS was examined in brain membranes from cerebellum and cortex of naive or chronically ethanol-treated C57B1 mice. In brain membranes of untreated animals, increasing concentrations of ethanol produced a dose-related inhibition of 35S-TBPS binding in the brain areas investigated. Additional studies showed that this effect of ethanol was due to a decreased affinity of 35S-TBPS for its binding sites. Chronic treatment of the animals with ethanol, which produced tolerance to and dependence on ethanol, did not alter ethanol's ability to inhibit the binding of 35S-TBPS. In naive animals, the in vitro addition of GABA or pentobarbital produced a pronounced inhibition of 35S-TBPS, both drugs being more potent in the cerebellum than in the cortex. Picrotoxin also produced a dose-dependent inhibition at 35S-TBPS, but was equally potent in the brain areas investigated. The inhibition by GABA or pentobarbital was not influenced by in vitro addition of a physiologically relevant concentration of ethanol (100 mM), whereas ethanol produced a significant increase in the IC50 values for picrotoxin both in the cortex and in the cerebellum. Furthermore, the inhibitory effects of GABA or pentobarbital on 35S-TBPS binding remained unchanged in animals chronically treated with ethanol for 7 days. Our data indicate that ethanol may affect the GABA receptor system through a rather specific interaction with the 35S-TBPS recognition site, but that this action of ethanol is not altered by the development of tolerance to and dependence on ethanol.

Clinical neuroendocrinology and neuropharmacology of alcohol withdrawal

A number of alcohol research groups have measured anterior and posterior pituitary hormones, the endogenous opiates, CNS peptides, and putative neurotransmitters during alcohol withdrawal. The data are often complex and contradictory, though a number of themes have emerged. Activity of the hypothalamic-pituitary-adrenal axis (HPA) is increased during chronic alcohol exposure and appears to remain altered for at least 2 to 4 weeks after cessation of drinking. There is increased turnover of norepinephrine and enhanced binding of CNS adrenergic receptors. By contrast, there are decreases in CNS activity of select endogenous opiates and GABA. Other CNS compounds that may play a role in alcohol withdrawal are prolactin, thyrotropin-releasing hormone (TRH), vasopressin, cyclic 3'5'-adenosine monophophate (cAMP), Delta-sleep-inducing peptide (DSIP), and iron. Despite many studies in humans and animals, the roles of CNS dopamine and serotonin in withdrawal remain unclear. A number of peptides, including cholecystokinin (CCK), neurotensin, and bombesin, have been shown to interact with the CNS actions of alcohol and may play a role in alcohol withdrawal. Inadequate work has been performed on acetylcholine (ACh), human growth hormone (HGH) and luteinizing hormone (LH). Studies of the recently identified GABA-benzodiazepine-barbituate receptor complex indicate that this system is likely to be involved in the pathophysiology of alcohol withdrawal. Perturbation studies with corticotropin-releasing factor (CRF) and TRH (with measures of ACTH and cortisol and TSH and prolactin, respectively), may identify patients with withdrawal-related autonomic dysfunction.

Enhancement of brain pyridoxal 5'-phosphate level following chronic ingestion of ethanol

The concentrations of pyridoxal 5'-phosphate in the brains of DBA/2J mice during the withdrawal period following chronic ethanol ingestion were measured fluorimetrically. The brain of the ethanol-withdrawn mouse contains 22.4 +/- 3.1% more pyridoxal 5'-phosphate than the brain of a control mouse. The enhanced susceptibility to epileptic seizures during the withdrawal phase may in part be due to the increased cerebral content of this coenzyme.

Biochemical basis of alcoholism: statements and hypotheses of present research

Experimental results and theoretical considerations on the biology of alcoholism are devoted to the following topics: genetically determined differences in metabolic tolerance; participation of the alternative alcohol metabolizing systems in chronic alcohol intake; genetically determined differences in functional tolerance of the CNS to the hypnotic effect of alcohol; cross tolerance between alcohol and centrally active drugs; dissociation of tolerance and cross tolerance from physical dependence; permanent effect of uncontrolled drinking behavior induced by alkaloid metabolites in the CNS; genetically determined alterations in the function of opiate receptors; and genetic predisposition to addiction due to innate endorphin deficiency. For the purpose of introducing the most important research teams and their main work, statements from selected publications of individual groups have been classified as to subject matter and summarized. Although the number for summary-quotations had to be restricted, the criterion for selection was the relevance to the etiology of alcoholism rather than consequences of alcohol drinking.

Ethanol withdrawal tremor does not interact with physostigmine-induced tremor in rat

Tremor in rats withdrawn from repeated ethanol administration was analyzed using an electronic device. The ethanol withdrawal tremor appeared in bursts during the first and second day of withdrawal and subsided at the third day of withdrawal. The frequency analysis showed that the mean frequency of withdrawal tremor was 6-7 Hz during the 48 hr observation period used. The frequency spectra of tremor induced by physostigmine (0.7 or 0.9 mg/kg) in control rats revealed that the tremoring frequency encompassed only a narrow peak, which temporarily decreased from 13 Hz to 11 Hz during the tremoring period. Arecoline (25 mg/kg) also induced tremor with a peak frequency at 13 Hz, but this tremor did not show any temporary decrease in peak frequency. The frequency analysis of tremor in ethanol withdrawn rats treated with physostigmine showed that the rats trembled at two frequencies, 6-7 Hz and 13 Hz. These two frequencies, each characteristic for one of the treatments, remained separate during the 48 hr observation period. As these two tremors did not interact with each other, it is suggested that these tremors are mediated by different mechanisms in the central nervous system. Thus it seems unlikely that the central muscarinic cholinergic system is involved in the genesis of tremor during ethanol withdrawal.

Brain cholinergic involvement in the rapid development of tolerance to the hypothermic action of ethanol

The enzymes of the cholinergic system have been investigated in discrete brain regions in mice treated with repeated injection of ethanol. Male mice kept under controlled environmental conditions were treated with ethanol (3 g/kg/day) for 3 days. Animals were sacrificed 1 hr after ethanol injections. Brain regions studied were cerebral cortex, cerebellum, midbrain, hypothalamus, medulla oblongata, amygdala, and hippocampus. The administration of a single dose of ethanol resulted in significant increase (P less than 0.05) in choline acetyltransferase (ChAT) activity in all different brain regions. Repeated injections of ethanol at the 2nd and 3rd day did not result in any further rise in ChAT activity of the brain regions studied except for the midbrain. The results also show that acetylcholinesterase (AChE) activities increased significantly (P less than 0.05) in the pons and hippocampus in acutely ethanol intoxicated animals. The repeated injection of ethanol resulted in significant increase in AChE activities of the cortex and the amygdala. Meanwhile, animals developed tolerance to the hypothermic action of ethanol after ethanol third injection. The results of the present investigation indicate that the rapid development of the hypothermic tolerance to ethanol might be mediated by the brain cholinergic system.