Neurotransmitter-receptor binding in various brain regions in ethanol-dependent rats

Acrylamide increases dopamine levels by affecting dopamine transport and metabolism related genes in the striatal dopaminergic system

Dopaminergic system dysfunction is proved to be a possible mechanism in acrylamide (ACR) -induced neurotoxicity. The neurotransmitter dopamine (DA) has an increasingly important role in the dopaminergic system. Thus, the goal of this study is to evaluate effects of ACR on dopamine and its metabolite levels, dopamine transport and metabolic gene expression in dopaminergic neurons. Male Sprague-Dawley (SD) rats were dosed orally with ACR at 0 (saline), 20, 30, and 40 mg/kg/day for 20 days. Splayed hind limbs, reduced tail flick time and abnormal gait which preceded other neurologic parameters were observed in the above rats. ACR significantly increased dopamine levels, decreased 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanilic acid (HVA) contents in an area dependent manner in rat striatum. Immunohistochemical staining of the striatum revealed that the number of tyrosine hydroxylase (TH) positive cells significantly increased, while monoamine oxidase (MAO) positive cells were drastically reduced, which was consistent with changes in their mRNA and protein expressions. In addition, dopamine transporter (DAT) and vesicular monoamine transporter 2 (VMAT2) expression levels were both down-regulated in the striatum. These results suggest that dopamine levels increase significantly in response to ACR, presumably due to changes in the dopamine transport and metabolism related genes expression in the striatal dopaminergic neurons.

Chronic voluntary ethanol intake hypersensitizes 5-HT(1A) autoreceptors in C57BL/6J mice

Alcoholism is a complex disorder involving, among others, the serotoninergic (5-HT) system, mainly regulated by 5-HT(1A) autoreceptors in the dorsal raphe nucleus. 5-HT(1A) autoreceptor desensitization induced by chronic 5-HT reuptake inactivation has been associated with a decrease in ethanol intake in mice. We investigated here whether, conversely, chronic ethanol intake could induce 5-HT(1A) autoreceptor supersensitivity, thereby contributing to the maintenance of high ethanol consumption. C57BL/6J mice were subjected to a progressive ethanol intake procedure in a free-choice paradigm (3-10% ethanol versus tap water; 21 days) and 5-HT(1A) autoreceptor functional state was assessed using different approaches. Acute administration of the 5-HT(1A) receptor agonist ipsapirone decreased the rate of tryptophan hydroxylation in striatum, and this effect was significantly larger (+75%) in mice that drank ethanol than in those drinking water. Furthermore, ethanol intake produced both an increased potency (+45%) of ipsapirone to inhibit the firing of 5-HT neurons, and a raise (+35%) in 5-HT(1A) autoreceptor-mediated stimulation of [(35)S]GTP-gamma-S binding in the dorsal raphe nucleus. These data showed that chronic voluntary ethanol intake in C57BL/6J mice induced 5-HT(1A) autoreceptor supersensitivity, at the origin of a 5-HT neurotransmission deficit, which might be causally related to the addictive effects of ethanol intake.

The combined effects of chronic ethanol/desipramine treatment on beta-adrenoceptor density and coupling efficiency in rat brain

Both ethanol and desipramine influence beta-adrenoceptor regulation. We reported previously that ethanol partially counteracted desipramine's effects on beta-adrenoceptor. Previous studies utilized beta-adrenoceptor radioligands that also bind to 5-HT1B receptors, thus, changes in 5-HT1B receptors could have confounded the results. The effects of chronic ethanol, desipramine and ethanol/desipramine treatment on beta-adrenoceptor coupling efficiency to Gs protein in rat brain were examined using 125I-iodocyanopindolol after blocking binding to 5-HT1B receptors. In the frontal cortex, ethanol uncoupled beta-adrenoceptor from GS. Desipramine decreased beta-adrenoceptor density, particularly in the high-conformational state, with no effect on coupling. In combined treatment, desipramine prevented ethanol-induced uncoupling. In the hippocampus, desipramine enhanced beta-adrenoceptor coupling, but ethanol had no effect. In combination with desipramine, ethanol enhanced desipramine-induced decrease in beta-adrenoceptor density in the high-conformational state, but uncoupled beta-adrenoceptors, an effect not observed with ethanol alone. These results suggest a complex interplay between ethanol and antidepressants in modulating beta-adrenoceptor function.

Molecular pathogenesis of alcohol withdrawal seizures: the modified lipid-protein interaction mechanism

The phrase alcohol withdrawal seizures (AWS) refers to seizures that result from the withdrawal of alcohol after a period of chronic alcohol administration. A mechanism of AWS is postulated, namely the modified lipid-protein interaction (MLPI) mechanism. This hypothesis is based upon an evaluation of the mechanisms of membrane fluidity, calcium channels, gamma-aminobutyric acid (GABA) and glutamate in the molecular pathogenesis of AWS. The mechanism hypothesizes that acute ethanol treatment alters the neuronal membrane lipids which then perturbs protein events, such as affecting the GABAA receptors, NMDA receptors and voltage-dependent Ca2+ channels synergistically or in combination. Subsequent adaptations in these systems occur after prolonged administration of ethanol. A sudden withdrawal of ethanol then leads to hyperexcitability which results in AWS.

Intra-amygdala muscimol decreases operant ethanol self-administration in dependent rats

Dependence is an important factor motivating continued alcohol use in human alcoholics. Development of a model of ethanol (EtOH) consumption in dependent animals would advance the understanding of reinforcement after chronic EtOH exposure and allow for the investigation of the neuropharmacological mechanisms mediating reinforcement in dependent versus nondependent animals. In the present study, rats were trained to lever press for 10% EtOH, surgically implanted with bilateral guide cannulae in the amygdala, and either made dependent on EtOH by exposure for 2 weeks to EtOH or exposed to air in identical vapor chambers. Upon removal, the rats were placed in operant boxes and allowed to respond on levers for 10% EtOH or water during a 12-hr period. Rats were removed briefly at approximately 6.5 hr for intra-amygdala injections of saline or the GABAA receptor agonist muscimol. After the test period, rats were returned to the vapor chambers for 4 days before retest. EtOH-dependent animals responded more for EtOH across the 12-hr test period than did air control nondependent rats; this difference became more pronounced with repeated test sessions. Intra-amygdala muscimol significantly decreased responding for EtOH in EtOH-dependent rats, but had no effect in nondependent controls. These data suggest that the reinforcing effects of EtOH and neurotransmitter pathways mediating reward are altered after the development of dependence, and they support the use of this paradigm for further investigations into the neuropharmacology of EtOH dependence.

Effects of chronic alcohol consumption and aging on dopamine D2 receptors in Fischer 344 rats

Aging and chronic alcohol consumption are each accompanied by significant changes in dopamine and dopamine receptors. This study extended previous work by investigating the combined effects of chronic alcoholism and aging on total dopamine D2 receptors in brain areas associated with the nigrostriatal and mesocorticolimbic systems. In addition, the effects of chronic alcohol consumption and aging on the high-affinity state of D2 receptors and their conversion to the low-affinity form is included. Quantitative autoradiography was used to assess [3H]spiperone-labeled D2 receptors in tissue sections from 5- to 14- and 24-month Fischer 344 rats that were pair-fed a control or 6.6% (v/v) ethanol-containing liquid diet for 6 weeks. In addition, D2 receptors were determined in rats given the control liquid diet ad libitum. The results of these experiments demonstrated age-related changes in the nigrostriatal system. There was an age-related loss of total dopamine D2 receptors in the rostral and caudal striatum (approximately 25% decrease in Bmax). This decline in D2 receptors may be associated with changes in motor function. Despite the age-related decline in D2 receptors, there were no significant differences in the proportion of striatal receptors in the high-affinity form or in their conversion to the low-affinity state. Both aging and chronic alcohol consumption produced significant changes in the concentration of D2 receptors in brain areas associated with the mesocorticolimbic system. That is, the specific binding of [3H]spiperone was decreased in the frontal cortex of aged rats. In addition, chronic alcoholism was associated with a significant increase (approximately 20%) in the Bmax for D2 receptors in the nucleus accumbens. Nonetheless, neither age nor chronic alcohol consumption altered the proportion of high-affinity D2 receptors in the nucleus accumbens or their conversion to the lower affinity state. The observed changes in D2 receptors in the frontal cortex and nucleus accumbens are of interest because of the involvement of the mesocorticolimbic dopamine areas in the rewarding properties of alcohol and other drugs of abuse. Although aging and chronic alcoholism both produced significant changes in dopamine D2 receptor concentrations, alcohol did not accentuate the age-related loss of D2 receptors. We cannot eliminate the possibility that a more prolonged exposure of higher ethanol dose may potentiate age-related changes in the dopaminergic system.

Ethanol withdrawal hyperexcitability in vitro is selectively decreased by a competitive NMDA receptor antagonist

Hippocampal slices were prepared immediately after withdrawal from chronic ethanol in vivo. The decreases in thresholds for production of single and multiple population spikes seen after the ethanol treatment were not evident when CGP39551 was included in the perfusion medium at 20 microM. The decrease in paired pulse potentiation seen during ethanol withdrawal, however, was not prevented by CGP39551. For comparison, the effects of CGP39551, at the same concentration, were examined on the changes in field potentials seen in control slices when the magnesium concentration in the bathing medium was lowered to 250 microM. The decreases in thresholds for multiple population spikes produced by the lowered magnesium were prevented, but not other changes including decreases in single spike thresholds. In addition, this 20 microM concentration of CGP39551 did not prevent epileptiform activity, measured by decreases in thresholds for production of single and multiple population spikes caused by addition of the GABAA antagonist, bicuculline, to control hippocampal slices.

Effects of chronic alcohol consumption and aging on dopamine D1 receptors in Fischer 344 rats

The present study examined the hypothesis that chronic alcoholism augments the age-related loss of dopamine D1 receptors. This hypothesis was investigated because previous studies reported that both aging and chronic alcoholism produce significant changes in dopaminergic systems, and because chronic alcoholism potentiates some age-related CNS losses. In addition, this study investigated the effects of aging on D1 receptors in animals 1 and 7 days after withdrawal from chronic ethanol. Quantitative autoradiography was used to measure [3H]SCH 23390 binding to D1 receptors in brain areas associated with both the nigrostriatal and mesocorticolimbic dopamine systems. Receptors were assessed in 5-, 14-, and 24-month-old male Fischer 344 rats that were pair-fed a control or 6.6% (v/v) ethanol-containing liquid diet for 6 weeks. The results of these studies demonstrated that aging is associated with a significant decline in D1 receptors in the rostral and caudal striatum, and substantia nigra of both control and ethanol-fed rats. These receptor changes in the nigrostriatal system may be associated with motor abnormalities. In addition, there was an age-related decline in D1 receptors in two brain areas of the mesocorticolimbic system: the nucleus accumbens and frontal cortex. The latter findings may be important because of the involvement of this system with the rewarding properties of ethanol and other drugs of abuse. There were no age-related differences in the response of D1 receptors to ethanol withdrawal in the caudal and rostral striatum, substantia nigra, and nucleus accumbens.(ABSTRACT TRUNCATED AT 250 WORDS)

Influences of housing conditions and ethanol intake on binding characteristics of D2, 5-HT1A, and benzodiazepine receptors of rats

The effects of different housing conditions and ethanol treatment (6 vol % in the drinking water) on the in vitro binding characteristics of striatal dopaminergic D2 ([3H]spiperone), hippocampal serotonergic 5-HT1A ([3H]8-OH-DPAT), and cortical benzodiazepine ([3H]flunitrazepam) receptors have been examined. Social deprivation due to contact caging, short- (1 day) and long-term isolation (5 weeks) yielded a significant decrease of striatal D2 receptor density with the greatest decrease after long-term isolation (-21% Bmax) without changes of Kd in comparison to group animals. The effect of ethanol on striatal D2 receptor density depended on the housing conditions. Whereas ethanol treatment reduced receptor density of group animals (down to 88%), chronic exposure to ethanol under long-term isolation elicited no significant alteration of D2 receptor density compared with group animals. Different housing and ethanol treatment had no effect on 5-HT1A receptor affinity and density. Alterations of benzodiazepine receptor density were not found, but social deprivation as well as ethanol treatment of group animals caused an increased affinity of [3H]flunitrazepam (reduced Kd value). These results indicate that different housing conditions of adult rats evoked significant alterations in D2 and benzodiazepine receptor binding assays, which were modified by ethanol treatment in the case of striatal D2 receptor density.

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.

Chronic effects of ethanol on central adenosine function of mice

Chronic ingestion of 5% ethanol had no significant effect on open field locomotor of NIH Swiss strain male mice, nor were the depressant effects of a non-selective adenosine receptor agonist, NECA, or the stimulant effects of a non-selective antagonist, caffeine significantly altered. The density of cerebral cortical A1-adenosine receptors and of nitrendipine binding sites on calcium channels were significantly increased after chronic ethanol, while the density of striatal A2a-adenosine receptors were unchanged. The locomotor stimulant effects of ethanol (2.5 g/kg) were slightly decreased after chronic ethanol, but were markedly reduced in mice after chronic caffeine ingestion. The results suggest some involvement of adenosine systems in the effects of ethanol.

Chronic ethanol produces a decreased sensitivity to the response-disruptive effects of GABA receptor complex antagonists

Disruption of responding for food reinforcement may reflect the motivational state subsequent to the onset of an aversive event and has previously been shown to be sensitive to spontaneous withdrawal from ethanol and precipitated opiate withdrawal. The purpose of this study was to attempt to precipitate ethanol withdrawal with bicuculline methiodide, a competitive GABAA receptor antagonist, and Ro 15-4513, a benzodiazepine inverse agonist. A quantitative operant measure of food-motivated behavior was used to evaluate the reactivity of the GABAA-benzodiazepine receptor complex during chronic ethanol treatment in rats. In the present study, rats were trained to lever-press for food reinforcement on a fixed ratio 15 schedule and then maintained for 2 weeks on a liquid diet containing 35% ethanol-derived calories or a control liquid diet that was prepared isocalorically with sucrose. Chronic ethanol treatment attenuated the disruptive effects on operant responding that were produced by bicuculline methiodide (100 ng ICV) and Ro 15-4513 (3 and 6 mg/kg). The inability of these drugs to "precipitate" EtOH withdrawal may reflect the noncompetitive interaction of ethanol with the GABA-benzodiazepine-ionophore receptor complex. These data are consistent with recent biochemical studies indicating that chronic ethanol treatment modulates the GABAA-benzodiazepine-ionophore receptor complex by altering the expression of specific molecular components and inhibiting the activity of the receptor complex.

Behavioral and neurochemical changes caused by repeated ethanol and cocaine administration

Combined cocaine and ethanol abuse has become increasingly popular, yet research on the behavioral and neurochemical interactions of these two substances is limited. Four groups of male rats received either daily cocaine (10 mg/kg, IP) or saline injections with either water (groups C and S) or only 15% ethanol to drink (groups CE and E). Initially, locomotor activity was increased equally by ethanol or cocaine and to the greatest extent by both. After 2 weeks of drug treatment, group C exhibited behavioral sensitization to cocaine, group E exhibited ethanol tolerance and group CE exhibited greater cocaine sensitization with no indication of ethanol tolerance. In support of enhanced sensitization to cocaine, amphetamine-stimulated 3H-dopamine (DA) release in striatum and D2 DA receptor binding in the nucleus accumbens (NAC) were increased in group CE compared to group C. In support of a loss of ethanol tolerance, increases in striatal D2 DA and 35S-TBPS binding seen in group E (which exhibited ethanol tolerance) were absent in group CE (which did not exhibit tolerance). Thus, the synergistic effect of ethanol and cocaine on behavior may be due to complex interactions of these two drugs both on DA and GABA transmission in mesolimbic and nigrostriatal areas.

Changes in intrinsic inhibition in isolated hippocampal slices during ethanol withdrawal; lack of correlation with withdrawal hyperexcitability

1. Intracellular recordings were made from pyramidal cells in area CA1 in mouse isolated hippocampal slices, after chronic ethanol treatment in vivo. 2. Fast i.p.s.ps were isolated by injection of the impaled neurones with QX314 (to block fast sodium currents and the slow i.p.s.p.) and stimulating the interneurones in the presence of the glutamatergic blockers, CNQX and APV. 3. The isolated fast-inhibitory postsynaptic potential (f.-i.p.s.p.) was measured at intervals during the 7 h withdrawal period. The reversal potential and sensitivity to bicuculline suggested that the isolated f.-i.p.s.p. was mediated by activation of the GABAA receptor-chloride ionophore complex. 4. Measurement of stimulus-response relationships for the f.-i.p.s.ps revealed an initial increase in the maximum size of the i.p.s.p., evoked from a membrane potential of -50 mV, seen at 2 h into ethanol withdrawal. This was attributed to a negative shift in the reversal potential, Ei.p.s.p., with no observed change in conductance, Gi.p.s.p. 5. No differences in f.-i.p.s.ps evoked during ethanol withdrawal or in control slices were seen at 4 h or 6 h. At these times, epileptiform activity was seen in previous field potential recordings. 6. Paired pulse depression of the f.-i.p.s.p. was significantly increased at 2 h into withdrawal, when a 150 ms pulse interval was used. No differences were seen at later times in the ethanol withdrawal period. 7. The results suggest that ethanol withdrawal hyperexcitability in isolated hippocampal slices is not caused by primary decreases in inhibition mediated by the GABAA receptor-chloride ionophore complex.4. Measurement of stimulus-response relationships for the f.-i.p.s.ps revealed an initial increase in the maximum size of the i.p.s.p., evoked from a membrane potential of - 50 mV, seen at 2 h into ethanol withdrawal. This was attributed to a negative shift in the reversal potential, Ejp.sp with no observed change in conductance, Gj ps p.5. No differences in f.-i.p.s.ps evoked during ethanol withdrawal or in control slices were seen at 4 h or 6 h. At these times, epileptiform activity was seen in previous field potential recordings.6. Paired pulse depression of the f.-i.p.s.p. was significantly increased at 2 h into withdrawal, when a 150 ms pulse interval was used. No differences were seen at later times in the ethanol withdrawal period.7. The results suggest that ethanol withdrawal hyperexcitability in isolated hippocampal slices is not caused by primary decreases in inhibition mediated by the GABAA receptor-chloride ionophore complex.The increase in the f.-i.p.s.p. during the initial stages of the withdrawal might prevent the overt expression of epileptiform activity at this time.

The effects of chronic ethanol consumption on the mesolimbic and nigrostriatal dopamine systems

Both the mesolimbic dopamine system, which is involved with the rewarding properties of several drugs of abuse, and the nigrostriatal dopamine system, which is involved with motor function, appear to be sensitive to the effects of ethanol. In order to determine which components of the mesolimbic and nigrostriatal dopamine systems are adversely affected by chronic ethanol consumption, we assessed dopamine and DOPAC (3,4-dihydroxyphenylacetic acid) concentration and D1 and D2 receptors in several dopaminergic brain areas. These studies demonstrated that consumption of a 6.6% (v/v) ethanol-containing lipid diet for 1 month affected several components of the mesolimbic dopamine system in 3-month-old Fisher 344 rats and fewer components of the nigrostriatal dopamine system. Specifically, there was a 1.6- to 2.6-fold increase in the concentration of DOPAC in the nucleus accumbens (NA), frontal cortex (FCX), ventral tegmental area (VTA), and substantia nigra (SN). While the increase in DOPAC in the FCX and VTA was paralleled by a similar increase in dopamine, there was a significant deficiency of dopamine in the SN. These results suggest that there is an increase in dopamine turnover in the FCX, VTA, NA, and SN, which is accompanied by increased dopamine synthesis in the former two regions. Studies of dopamine receptors in control and ethanol-fed rats demonstrated a 25% loss of D1 receptors in the NA. No significant differences were found in D1 receptors in the striatum or globus pallidus. In addition, there were no differences in the number of total D2 receptors or in the conversion of the high to low affinity state of D2 receptors in the nucleus accumbens and striatum.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Neuroendocrine responses to serotonergic agents in alcoholics

Previous studies have suggested a possible deficit in serotonergic function in alcoholism. In order to further assess the serotonergic system in alcoholism, the plasma cortisol and prolactin (PRL) responses following 6-chloro-2-[1-piperazinyl]pyrazine (MK-212), a direct-acting serotonin2 (5-HT2)/5-HT1c receptor agonist, L-5-hydroxytryptophan (L-5-HTP), a precursor of 5-HT, and placebo were compared in male alcoholics and normal controls. The increase in plasma cortisol following L-5-HTP was significantly lower in the alcoholic subjects compared with the normal controls. The plasma PRL, but not the plasma cortisol response, following MK-212 was also significantly lower in the alcoholics. L-5-HTP had no significant effect on plasma PRL levels in either group. The basal plasma cortisol and PRL concentrations of the alcoholics and normal controls were not significantly different. These data are consistent with previous reports of a serotonergic abnormality in alcoholism.

Altered pineal serotonin binding in some suicides

Serotonergic abnormalities have been regularly reported in the brains of suicide victims. Because of evidence that pineal function is altered in depressed subjects and that serotonin-releasing axons may innervate the pineal, we assayed tritiated serotonin binding in a series of control and suicide pineals. High affinity binding was present, and there were apparent differences between some suicides and controls.

Ethanol potentiates serotonin stimulated inositol lipid metabolism in primary astroglial cell cultures

Serotonin-stimulated activation of phospholipase C in primary astroglial cell cultures was studied as a mean of evaluating the effect of acute ethanol exposition on this signal transduction system. The addition of 50-150 mM ethanol prior to stimulation with 10(-5) M serotonin led to a potentiation of the serotonin-induced [3H]-inositol phosphate formation and an increased incorporation of [3H]-inositol into the three phosphoinositides studied. This potentiating effect of ethanol was observed only when ethanol was added together with serotonin. No stimulatory effect of ethanol per se was found. Furthermore, ethanol had no effect on arginine-vasopressin, bradykinin or phenylephrine stimulated inositol lipid metabolism.

Ethanol does not affect serotonin receptor binding in rodent brain

The effects of ethanol on serotonin (5-hydroxytryptamine, 5-HT) receptor binding in rat and mouse brain were determined under in vitro conditions and in mouse brain following seven days of ethanol ingestion. 5-HT1A receptor characteristics were measured utilizing the agonist [3H]8-hydroxy-2-(di-n-propylamino)tetralin ([ 3H]DPAT), and 5HT2 receptor-binding studies utilized the antagonist [3H]ketanserin. At the highest concentration of ethanol tested in vitro (680 mM), there was only 25% inhibition of [3H]DPAT binding in rat and mouse brain and 14% inhibition of [3H]ketanserin binding in rat brain. Effects of an anesthetic concentration of ethanol (100 mM) on agonist binding in the presence and absence of the guanine nucleotide GTP were also evaluated in vitro in mouse brain. In no case did ethanol (100 mM) significantly affect 5-HT1A or 5-HT2 receptor-binding characteristics. When 5-HT receptor characteristics were measured after mice consumed ethanol for seven days, there was no change in either 5-HT1A or 5-HT2 receptor-binding properties in any of the brain areas examined.

Improvement of inpatient treatment of the alcoholic as a function of neurotransmitter restoration: a pilot study

We report results of a double-blind evaluation of the nutritional supplement SAAVE for facilitating improvement in a 30-day inpatient alcohol and drug rehabilitation center. SAAVE is uniquely designed to elevate levels of enkephalin(s), serotonin, catecholamines, and GABA, which are believed to be functionally deficient in alcoholics. Twenty-two patients were studied. The SAAVE patients, as compared to the control group (a) had a lower BUD (building up to drink) score, 1 vs 2; (b) required no PRN benzodiazepines, 0% vs 94%; (c) ceased tremoring at 72 h, as compared to 96 h; and (d) had no severe depression on the MMPI, in contrast to 24% of control group. These preliminary data suggest that SAAVE is a valuable adjunct to therapy by aiding the patient's physical adjustment to a detoxified state while facilitating a more positive response to behavioral therapy.

Decrease in the number of rat brain dopamine and muscarinic receptors after chronic alcohol intake

The effect of 32 weeks' alcohol treatment on the number and affinity of dopamine and muscarinic receptor sites in rat striatum were measured using 3H-spiperone and 3H-quinuclidinylbenzilate (3H-QNB) as radioligands. The number of dopamine receptor sites was 38 per cent and the number of muscarinic receptor sites 36 per cent lower in the alcohol group than in control rats. The differences in receptor affinities were less marked. In conclusion, a long-term alcohol intake with rather moderate doses seems to induce a pronounced down-regulation in dopamine and muscarinic receptor systems in rat striatum.

Differential effects of chronic ethanol on apomorphine-induced locomotion, climbing and aggression in rats

Male Wistar rats were tested for apomorphine-induced locomotion, climbing and aggression after 3 week's intragastric ethanol (EtOH) treatment, 5 g/kg as 20% solution daily. The ability of apomorphine (APO) to elicit rearing (1 mg/kg i.p.) and climbing (0.5 mg/kg i.p.) was significantly suppressed in EtOH withdrawn animals. General locomotor activity in response to 1 mg/kg of APO i.p. did not differ between control and EtOH-treated groups. Affective aggression was checked in pairs of low-aggressive rats, i.e. resistant to the aggression inducing action of 10 mg/kg APO. No symptoms of aggression appeared in control animals whereas EtOH administered rats responded with marked aggression to APO. The different effect of chronic EtOH on responsiveness to APO in three behavioral models is discussed in terms of varying involvement of dopaminergic systems and receptors in behavioral phenomena as well as their susceptibility to prolonged EtOH.

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.

The effect of ethanol and haloperidol on dopamine receptor (D2) density

The study was performed to investigate the influence of ethanol on haloperidol-induced changes of the dopamine (D2) receptors in rat striatal membrane preparations. Subchronic administration of the neuroleptic in the drinking water resulted in an increase of the number of binding sites in a dose-dependent manner. Simultaneous treatment with both haloperidol and ethanol prevented the rise of D2 receptors.

Central nervous system prostaglandins and ethanol

There is growing interest in the effect of ethanol on cellular membranes, generally, and neuronal membrane systems, in particular. Perturbations of membranes have led to numerous enzymatically mediated processes, one of which is prostaglandin production. This paper reviews the nature and role of prostaglandins in the central nervous system, and what is known about the effect of ethanol on prostaglandin production in brain. Areas of central nervous system physiological function in which prostaglandins may mediate the actions of ethanol are discussed. Methodological considerations and future directions for research in the area of ethanol and prostaglandins are highlighted.

Effect of ethanol on receptor-stimulated phosphatidic acid and polyphosphoinositide metabolism in mouse brain

The effects of chronic ethanol consumption as well as the effects of ethanol added in vitro on phosphoinositide metabolism were determined in mouse forebrain. [32P] incorporation into synaptosomal phosphatidic acid (PhA) was stimulated through both M1 muscarinic cholinergic and alpha 1 adrenergic receptor activation. Similarly, [3H]inositol 1-PO4 accumulation in brain slices was stimulated through these same receptors, but could also be stimulated by histamine1 receptor activation. In mice made physically dependent to ethanol, the magnitude of receptor-mediated [32P] incorporation in PhA did not differ from that of control animals. However, ethanol (100mM) added in vitro to synaptosomes from control mice significantly inhibited the carbamylcholine stimulated PhA response, but had no effect on the response to norepinephrine. Carbamylcholine stimulated [32P] incorporation into PhA, however, was no longer significantly inhibited by the addition of 100mM ethanol to synaptosomes from physically dependent-tolerant animals indicating that a cellular tolerance had developed. In contrast, receptor mediated [3H]inositol 1-PO4 accumulation in brain slices was not significantly affected by either chronic ethanol treatment or the in vitro addition of ethanol as high as 200mM. It is concluded that the muscarinic cholinergic stimulation of [32P] incorporation into PhA, but not [3H]inositol 1-PO4 accumulation is relatively more sensitive to the direct effects of ethanol than are the other receptor mediated phospholipid responses examined in the present investigation and that this sensitivity is lost in animals made behaviorally tolerant and physically dependent to ethanol.

Changes in dopamine receptor sensitivity in humans after heavy alcohol intake

Dopamine (DA) sensitivity, assessed through maximal growth hormone (GH) response to stimulation by apomorphine (APO) (0.18-0.24 mg iv) was studied in 16 chronic alcoholics newly admitted after a period of heavy alcohol intake. Repeated hormonal tests were thereafter performed during a 2-month period under strictly controlled conditions to avoid relapse into alcohol consumption. Eight healthy volunteers with alcohol consumption slightly less than that of the general population were used as controls. It was found that DA sensitivity in the early abstinence phase was higher than later in the 2-month recovery period but not significantly different from control values. The relatively higher DA sensitivity in the early abstinence phase might be responsible for a lower threshold for psychotic symptoms and neuroleptic-induced extrapyramidal side effects. The results of this study give further evidence of a prolonged recovery phase after heavy alcohol intake.

Acquisition of behaviourally augmented tolerance to ethanol and its relationship to muscarinic receptors

Two groups of adult male rats were injected daily with ethanol (1.5 g/kg IP in 15% w/v solution) either before (the behaviourally augmented tolerant group) or after (the physiologically tolerant group) being placed in operant chambers. The control groups received daily isotonic saline injections either before or after the operant task. When challenged with ethanol (2.5 g/kg) on day 30 prior to the operant task, the control group was most impaired, while the behaviourally augmented tolerant group was significantly less impaired than the physiologically tolerant group. The two ethanol-treated groups were impaired to the same extent when challenged on day 60. Partial generalization of this behavioural tolerance to ethanol was observed, as the behaviourally augmented tolerant group was less impaired than the physiologically tolerant group for a tail flick response to painful stimuli after an ethanol challenge on day 30. However, the two ethanol-treated groups exhibited similar impairments of locomotor activity after an ethanol challenge on day 40. No differences in muscarinic receptor binding among the control and two ethanol-treated groups were found. These findings demonstrate that behaviourally augmented tolerance to ethanol may be partially generalizable but is unrelated to changes in muscarinic cholinergic receptors.

Behavioural plasticity and the cholinergic system

Evidence for the involvement of the cholinergic system in behavioural plasticity is reviewed by considering three forms of behavioural plasticity: habituation, learning and memory, and tolerance development. Although the cholinergic system may modulate the response tendencies of an animal, it does not appear to be involved in the process of habituation. A number of studies have indicated that the cholinergic system may be involved in learning and memory processes in infrahuman animals. In general, cholinergic antagonists tend to disrupt memory while agonists may, under the appropriate conditions, facilitate memory. Recent studies have pointed to a relation between dysfunctions of the cholinergic system and dysfunctions of memory in aged animals. Studies of tolerance development suggest that the cholinergic system may undergo plastic changes which may underlie the development of tolerance to some drugs, with receptor alterations being the most reproducible finding. However, more work is necessary to establish the degree of plasticity. The cholinergic system also appears to be involved in learning and memory processes in humans. However, attempts to correct the memory deficits in aged humans by manipulating the cholinergic system have met with limited success. The reasons for this lack of success are briefly considered.

Tolerance, physical dependence and changes in muscarinic receptor binding sites after chronic ethanol treatment in the rat

Rats were treated with ethanol in the drinking water for 73-75 weeks. The daily drinking periods were restricted to only 2x1 h to get significant ethanol blood concentrations. After the end of the ethanol treatment (last day of treatment denoted day 0 of the abstinence) tolerance to sedatives were recorded with a hexobarbital threshold method, convulsions recorded with jiggle cages, and muscarinic receptor binding sites determined with 3H-quinuclidinyl benzilate. Tolerance to hexobarbital was found to have a maximum on day 8 in the abstinence while convulsions recorded from the rats participating in the hexobarbital threshold determinations had a maximum on day 14. Atropine administered as a single dose on day 8 decreased the tolerance to hexobarbital on that day and seemed to reduce the number of convulsions on the following days. Muscarinic receptor sites were significantly increased in the striatum on day 8 of the abstinence at the time of maximal tolerance, This increase in muscarinic receptors was less in rats which had had convulsions during the abstinence before sacrifice. Thus the results indicate that cholinergic mechanisms are involved in the changes seen during the abstinence after chronic ethanol exposure.