Effects of Chronic Ethanol Consumption and Aging on 5-HT2A Receptors and 5-HT Reuptake Sites

The serotonergic system in brain is adversely affected by both aging and chronic ethanol consumption. The present study examined the combined effects of aging and chronic ethanol consumption on two components of the serotonergic system. Serotonin (5-HT) reuptake sites and 5-HT_2A receptors were quantitated in brain areas of 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 on a chronic basis. The regions examined include those containing the cell bodies and projections of serotonergic neurons. These experiments demonstrated the sensitivity of the serotonergic system of male Fischer 344 rats to both aging and chronic ethanol consumption. In control rats, aging was associated with a decline in the concentration of 5-HT_2A receptors in the nucleus accumbens and four cortical regions: frontal, parietal, piriform, and cingulate cortex. 5-HT_2A receptors were also reduced in the frontal, parietal, and cingulate cortex of aged ethanol-fed rats. In contrast, 5-HT reuptake sites were increased in older rats in the frontal cortex, nucleus accumbens, amygdala, and CA3 region of the hippocampus. If comparable changes in 5-HT_2A receptors and 5-HT reuptake sites occur in elderly humans, they may contribute to ethanol consumption, and lead to cognitive and other age-related problems. These changes may also alter the effectiveness of serotonergic drugs used in the treatment of alcoholism and mental disorders. The effects of chronic ethanol consumption were more limited. The only significant ethanol effect was an increase of 5-HT_2A receptors in the nucleus accumbens of 5-month-old ethanol-fed rats.     

Analysis of the 5-HT2 Receptor Ligands Dimethoxy-4-indophenyl-2-aminopropane and Ketanserin in Ethanol Discriminations

Previous studies have suggested a modulatory role of the 5-HT₂ receptor system in the behavioral effects of ethanol. The present study examined the discriminative stimulus effects of the 5-HT_2A/2C agonist (–)-dimethoxy-4-indophenly-2-aminopropane (DOI) and the 5-HT_2A antagonist ketanserin in rats trained to discriminate either 1.5 g/kg of ethanol from water (intragastrically, n = 7) or 2.0 g/kg of ethanol from water (intragastrically, n = 8). In substitution tests, neither DOI (0.3 to 1.0 mg/kg, ip) nor ketanserin (3.0 to 17.0 mg/kg, ip) produced discriminative stimulus effects similar to either training dose of ethanol, although decreases in rates of responding were significant at the highest doses tested. Likewise, when given in combination with ethanol, neither 5-HT₂ ligand shifted the ethanol-dose response determination in either the 1.5 or 2.0 g/kg ethanol training groups. DOI in combination with ethanol did not alter rates of responding, whereas ketanserin in combination with ethanol significantly decreased response rates. Thus, the 5-HT_2A receptor ligands do not appreciably affect the discriminative stimulus effects of ethanol, in contrast to previous results with 5-HT_1B ligands.     

The 5-HT3 Antagonist MDL-72222 Exacerbates Ethanol Withdrawal Seizures in Mice

Ethanol-dependent mice were treated with the 5-HT₃ antagonist MDL 72222 after withdrawal from ethanol. Treatment with unit doses (0, 5.6, 10, and 17.0 mg/kg) of MDL 72222 at 0, 4, and 7 hr after withdrawal dose-dependently exacerbated the severity of ethanol withdrawal seizures. Treatment with a single dose (17 mg/kg) of MDL 72222 at 5 hr after withdrawal also exacerbated the severity of ethanol withdrawal seizures. Ethanol naive mice treated with MDL 72222 (56 mg/kg) did not display any seizures. Treatment with another 5-HT₃ antagonist, ICS 205-930 (23 and 46 mg/kg), or the 5- HT₂ receptor antagonist ketanserin, did not affect ethanol withdrawal seizures. The findings suggest MDL 72222 selectively enhances sensitivity to withdrawal seizures following chronic ethanol exposure.     

Possibility of 5-HT3 Receptor Involvement in Alcohol Dependence: A Microdialysis Study of Nucleus Accumbens Dopamine and Serotonin Release in Rats with Chronic Alcohol Consumption

The present study was performed to examine the involvement of serotonin-3 (5-HT3) receptors in the rat nucleus accumbens (ACC) in alcohol dependence. In alcohol-treated rats, perfusion of 40 mM K⁺ and 100 mM ethanol (EtOH) through the microdialysis probe increased the extracellular levels of ACC dopamine (DA), compared with controls. Perfusion of the serotonin (5-HT) uptake inhibitor sertlarine enhanced the extracellular levels of ACC 5-HT in both groups. Increased 5-HT availability in the synaptic clefts on the ACC further activated ACC DA release in the alcohol-treated rats, in comparison with controls. In the final experiments, perfusion of the 5.0 μ M 5-HT₃ receptor agonist 2-methyl-5-HT (2-Me-5-HT) through the microdialysis probe enhanced the extracellular levels of ACC DA. Magnitude of 2-Me-5-HT-induced DA release was significantly higher in alcohol-treated rats than in controls. On the other hand, 40 mM K⁺- and 100 mM EtOH-induced extracellular 5-HT release in alcohol-treated rats were markedly inhibited. These results show that (1) chronic alcohol intake increases the sensitivity of 5-HT₃ receptors, (2) 5-HT₃ receptors regulate DA release in the ACC, (3) the dopaminergic neuronal systems associated with 5-HT₃ ionophore in the ACC were upregulated after chronic alcohol exposure, and (4) chronic alcohol intake desensitizes the serotonergic neuronal systems in rat ACC. These findings suggest that neurochemical functions of 5-HT₃ receptors in regulating DA release in the ACC after alcohol exposure compensate for the dysfunction of serotonergic activity to restore the original properties in processing alcohol tolerance and that the development of alcohol dependence may be mediated by ACC 5-HT₃ receptors.     

Additive Reduction of Alcohol Drinking by 5-HT1A Antagonist WAY 100635 and Serotonin Uptake Blocker Fluoxetine in Alcohol-Preferring P Rats

We found previously that alcohol-preferring (P) rats have fewer serotonin (5-HT) neurons and fibers in key brain regions than alcoholnonpreferring (NP) rats. Because 5-HT uptake blockers increase synaptic 5-HT content and 5-HT_1A receptor antagonists increase 5-HT release by disinhibiting 5-HT autoinnervation, in the present study, our intent was to determine whether increased synaptic 5-HT content and/or 5-HT release in P rats would effectively reduce alcohol consumption. In experiment 1, the 5-HT antagonist WAY 100635 (WAY) was tested on adult female P rats maintained on 24-hr free-choice access to ethanol (10% v/v) and water. Twice daily doses of WAY (0.05, 0.1, 0.5, and 1.0 mg/kg, subcutaneously) were administered to each rat in a counterbalanced order. Baseline ethanol intake, derived from the mean ethanol intakes of the three previous non-drug days, was approximately 8 g/kg/day. Results indicated that 0.05,0.1, and 0.5 mg/kg doses of WAY reduced 24-hr ethanol drinking by 25-30% ( p < 0.01) without affecting 24-hr water intake or body weight In the second experiment, the effects of WAY (0.5 mg/kg), fluoxetine (1.0 mg/kg), or a combination of both were tested in another group of female P rats. WAY and fluoxetine, each alone, reduced ethanol drinking by around 20% and, when combined, decreased ethanol intake by 50%, whereas the body weight and the total fluid intake were not significantly affected. Taken together, these results indicate that both fluoxetine and WAY preferentially reduce ethanol drinking in the P line of rats and, when administered together, reduce ethanol intake in an additive manner. It is proposed that coadministration of these two compounds with distinct mechanisms of action may be a new strategy for reducing alcohol intake.     

Reduced Sensitivity to Ethanol Reward, But Not Ethanol Aversion, in Mice Lacking 5=HT1B Receptors

Various serotonergic receptor systems are thought to influence the motivational effects of ethanol. This experiment characterized the acquisition of ethanol-induced conditioned taste aversion and ethanol-induced conditioned place preference in mutant knockout mice lacking 5-HT_1B receptors. In the taste conditioning procedure, adult homozygous knockout mice (-/-) and homozygous wild-type mice (+/+) received access to 0.2 M NaCl solution, followed immediately by intraperitoneal injection of 0 to 4 g/kg of ethanol. Ethanol produced dose-dependent conditioned taste aversion that was the same in both genotypes. In the place conditioning procedure, knockout and wild-type mice received six pairings of a tactile stimulus with ethanol (2 g/kg, ip). A different tactile stimulus was paired with saline. Ethanol produced increases in locomotor activity, with wild-type mice showing higher levels of ethanol-stimulated activity than knockout mice during conditioning trials 5 and 6. Wild-type mice demonstrated conditioned place preference for the ethanol-paired stimulus. In contrast, knockout mice showed no evidence of place conditioning. These results are generally consistent with an important role for serotonergic systems in ethanol reward and specifically indicate that 5-HT_1b receptors are important for ethanol's rewarding effects but not for ethanol's aversive effects.     

Nocturnal plasma melatonin concentrations in healthy volunteers: Effect of single doses of d-fenfluramine, paroxetine, and ipsapirone

Abstract: The effect on nocturnal melatonin secretion of acute administration of the indirectly acting serotonin (5-HT) receptor agonists d-fenfluramine (30 mg) and paroxetine (20 mg) and a partial 5-HT_1A receptor agonist ipsapirone (20 mg) was investigated in healthy male volunteers and compared to a placebo condition. Each subject (n=8) received each drug on one occasion over a 4 week study period, with drug administration separated by 1 week. A randomized, counter-balanced design was used. Drugs or placebo were administered at 2,000 hours in the light, and all blood samples were collected throughout the night in the dark at regular intervals until 0600 hours. Neither d-fenfluramine, paroxetine, or ipsapirone following acute dosage had a statistically significant effect on nocturnal melatonin synthesis. The lack of effect seen with d-fenfluramine, paroxetine, and ipsapirone may be due to limitations imposed by the dose requirements.     

Effects of Maternal Ethanol Consumption and Buspirone Treatment on Dopamine and Norepinephrine Reuptake Sites and D1 Receptors in Offspring

Previously, it was shown that in utero ethanol exposure results in decreased serotonin (5-HT) and altered concentrations of 5-HT reuptake sites and 5-HT_1A receptors in fetal and/or postnatal rats. Because fetal 5-HT is an essential trophic factor, this laboratory previously investigated the hypotheses that the early ethanol-associated 5-HT deficit contributed to subsequent development abnormalities in the serotonergic system and that the effects of the fetal 5-HT deficit could be prevented by maternal treatment with buspirone, a 5-HT_1A receptor agonist. The present report determined the effects of maternal treatment with buspirone on two other neurotransmitter systems in the developing offspring of ethanol-fed dams: dopamine (DA) and norepinephrine reuptake sites and D1 receptors in postnatal day 19 offspring of control and ethanol-fed dams, that received daily injections of saline or 4.5 mg/kg buspirone. These investigations found that in utero ethanol exposure significantly decreased norepinephrine reuptake sites in the dorsomedial hypothalamic nucleus and anteroventral thalamic nucleus. There was also an ethanol effect in the dorsal raphe. D1 receptors were moderately increased (5–10% increase) in the striaturn, and DA reuptake sites were unchanged in PN19 ethanol-exposed offspring. No other significant ethanol-related effects were noted. Maternal buspirone treatment did not adversely affect the concentration of DA reuptake sites or D1 receptors in control rats. Thus, whereas buspirone exerts protective effects on the developing 5-HT system of ethanol-exposed rats, it does not appear to damage the development of the DA system. Maternal buspirone produced only one significant abnormality in control offspring; it resulted in a significant reduction of norepinephrine reuptake sites in the DR.     

Serologic and Immunochemical Characterization of Ax Blood

Serologic and immunochemical analyses of A_x bloods have defined a probable specific antibody to the A_x antigen in group O serum. Anti-A_x activity was found to be in 19S (β_2M, γ_1A) and β_2A (γ_1A) globulin fractions but not in the 7S (γ₂) globulin of human group O sera.

Résumé

Les analyses immuno-chimiques et sérologiques des sangs A_x ont permis de déceler un anticorps spécifique contre l'antigène A_x dans les sérums de sang de groupe O. L'activité anti-A_x a été trouvée dans les fractions de globulines 19S (β_2M, γ_1A) et β_2A (γ_1A) mais pas dans la fraction des globulines 7S (γ₂) des sérums des personnes de groupe O.

Zusammenfassung

Anläßlich der serologischen und immunochemischen Analyse von A_x-Blutproben gelang es zu zeigen, daß im O-Serum offenbar ein spezifischer Antikörper gegen das A_x-Antigen enthalten ist. Die Anti-A_x-Aktivität fand sich in den 19S (β_2M, γ_1A) und β_2A (γ_1A) Globulinfraktionen, nicht aber in der 7S (γ₂) Globulinfraktion der menschlichen O-Seren.     

The reinforcing properties of salsolinol in the ventral tegmental area: evidence for regional heterogeneity and the involvement of serotonin and dopamine

Background:  Salsolinol (SAL), the condensation product of acetaldehyde and dopamine, may be a factor contributing to alcohol abuse. Previous research indicated that both ethanol and acetaldehyde are self-administered into the posterior ventral tegmental area (VTA). The current study examined SAL self-infusions into the VTA, and determined the involvement of dopamine neurons and 5-HT₃ receptors in this process.
Methods:  The intracranial self-administration technique was used to determine the self-infusion of SAL into the VTA of adult, male Wistar rats. The rats were placed in 2-lever (active and inactive) experimental chambers, and allowed to respond for the self-infusion of 0, 0.03, 0.1, 0.3, 1.0 or 3.0 μM SAL into the posterior or anterior VTA. In a second experiment, rats self-administered 0.3 μM SAL for the initial 4 sessions, co-administered SAL with ICS-205,930 (a 5-HT₃ receptor antagonist) or quinpirole (a D_2,3 receptor agonist) for sessions 5 and 6, and then only 0.3 μM SAL for session 7.
Results:  Wistar rats, given 0.03 to 0.3 μM SAL, received more infusions per session than did the group given artificial cerebrospinal fluid (aCSF) alone (e.g., 41 infusions for 0.1 μM SAL versus 9 infusions for the aCSF group), and responded more on the active than inactive lever. These effects were observed in the posterior but not in anterior VTA. Co-infusion of 100 μM ICS-205,930, or quinpirole significantly reduced self-infusions and active lever responding.
Conclusions:  SAL produces reinforcing effects in the posterior VTA of Wistar rats, and these effects are mediated by activation of DA neurons and local 5-HT₃ receptors.     

The α1-Adrenergic Receptor Antagonist, Prazosin, Reduces Alcohol Drinking in Alcohol-Preferring (P) Rats

Background:  Preliminary evidence suggest that noradrenergic signaling may play a role in mediating alcohol drinking behavior in both humans and rats. Accordingly, we tested the hypothesis that blockade of α₁-adrenergic receptors will suppress alcohol drinking in rats selectively bred for alcohol preference (P line).
Methods:  Adult male P rats were given 24-hour access to food and water and scheduled access to a 15% (v/v) alcohol solution for 2 hours daily. Rats were injected IP with the α₁-adrenergic receptor antagonist, prazosin (0, 0.5, 1.0, 1.5, or 2.0 mg/kg body weight), once a day at 15 minutes prior to onset of the daily 2-hour 2-bottle choice, alcohol versus water, access period for 2 consecutive days and then 3 weeks later for 5 consecutive days.
Results:  Prazosin significantly reduced ( p  < 0.01) alcohol intake during the initial 2 daily administrations, and this reduction of alcohol intake was maintained for 5 consecutive days by daily prazosin treatment in the subsequent more prolonged trial ( p  < 0.05). The prazosin-induced reduction of alcohol intake was not dependent upon drug-induced motor impairment since increases in water drinking ( p  < 0.05) were exhibited during the 2-hour access periods during both 2- and 5-day prazosin treatment.
Conclusions:  The results indicate that the noradrenergic system plays a role in mediating alcohol drinking in rats of the P line and suggest that prazosin—a safe, well-characterized, and well-tolerated drug—may be an effective pharmacotherapeutic agent for the treatment of alcohol use disorders.     

Captopril and Hydrochlorothiazide (Capozide®) Combine to Enhance the Reduction in Voluntary Alcohol Intake in Rats

The effect of Capozide®, the combination of captopril with a hydrochlorothiazide diuretic, on voluntary alcohol intake was assessed in two experiments. In experiment 1 naive rats who were maintained on ad libitum food and water were given daily 40-min access to a 6% (w/v) alcohol solution and water. Daily intraperitoneal injections of captopril (10 mg/kg) reduced alcohol intake, but the combination of captopril (5 and 10 mg/kg) and hydrochlorothiazide (2.5, 5, and 10 mg/kg) enhanced the reduction in intake. In experiment 2, captopril alone, hydrochlorothiazide alone, and the combination of captopril and hydrochlorothiazide were again administered daily in the limited access procedure. Captopril (10 mg/kg) again reduced alcohol intake as did all three doses of hydrochlorothiazide (2.5, 5, and 10 mg/kg). Compared with the individual effects of captopril and hydrochlorothiazide, Capozide® exerted a supra-additive reduction in alcohol intake. These effects were not due to drug-induced changes in the pharmacokinetics of alcohol. Taken together these results demonstrate an enhanced potency of Capozide® in suppressing alcohol intake and invite their testing in a population of hypertensive alcoholics and alcohol abusers.     

Serotonin2C Receptors and Serotonin2C Receptor-Mediated Phosphoinositide Hydrolysis in the Brain of Alcohol-Preferring and Alcohol-Nonpreferring Rats

To examine the role of serotonin_2C (5HT_2C) receptors in alcohol drinking behavior, the binding indices of 5HT_2C receptors were determined in various brain regions of alcohol-preferring (P) and alcohol-nonpreferring (NP) rats. 5HT_2C receptor-mediated phosphoinositide hydrolysis in the choroid plexus of P and NP rats was also determined. It was observed that the densities of 5HT_2C receptors are significantly higher in the hippocampus, the amygdala, and the choroid plexus, but not in the cortex of P rats compared with NP rats. The K _d values of [³H]mesulergine binding to 5HT_2C receptors were not different in these brain regions of P rats compared with NP rats. It was also observed that 5HT-stimulated [³H]inositol 1-phosphate formation was significantly higher in the choroid plexus of P rats compared with NP rats. The results of this study indicate that the numbers of 5HT_2C receptors are higher in the hippocampus, the amygdala, and the choroid plexus, and that 5HT_2C receptor-mediated phosphoinositide hydrolysis is more elevated in the choroid plexus of P rats compared with NP rats. Thus, it seems from these results that increased 5HT_2C receptors may be involved in the genetic vulnerability to alcohol drinking behavior.     

Dopamine D2 Receptor Gene Expression in Rat Lines Selected for Differences in Voluntary Alcohol Consumption

A selective breeding program has led to the establishment of the alcohol-preferring AA (Alko, Alcohol) and alcohol-avoiding ANA (Alko, Nonalcohol) rat lines. To reveal putative baseline differences in dopamine receptor gene expression and dopamine receptor binding profile in the AA and ANA rat lines, we assessed striatal D₂ mRNA levels in these two rat lines. Autoradiographical studies on dopamine D₁ and D₂ receptors in the striatum and nucleus accumbens were also performed with [³H]SCH 23390 and [¹²⁵I]iodosulpiride/[³H]spiperone, respectively. The baseline differences in D₁ or D₂ receptor binding and D₂ receptor gene expression between AA and ANA rat lines are marginal, and are not likely to play a role in the genetic background of the differential alcohol drinking behavior of these rat lines.     

p16INK4A gene homozygous deletions in human acute leukaemias with alterations of chromosome 9

Acute leukaemias are characterized by non-random chromosomal aberrations which are often strictly related to the inactivation of tumour suppressor genes (TSGs). Alterations at the short arm of chromosome 9 have been reported in a remarkable percentage of acute lymphoblastic leukaemias (ALL) and have been suggested to cause the loss of activity of the putative TSG, p16^INK4A (MTS1/CDKN2) gene. In order to evaluate the correlation between this gene inactivation and visible cytogenetic abnormalities, we have investigated p16^INK4A homozygous gene deletions in 10 paediatric acute leukaemias of different cell lineages which demonstrated karyotype aberrations involving chromosome 9. Moreover, the dimension of the genetic alteration was evaluated by studying the loss of heterozygosity of two highly polymorphic markers of chromosome 9p, namely α-interferon (IFNA) and D9S104, and the deletion of 5'-methylthioadenosine phosphorylase (MTAPase) gene. Finally, the deletion of a gene belonging to p16^INK4A family, the p18 gene, was analysed in these acute leukaemias. Our results demonstrated that: (i) the biallelic loss of p16^INK4A gene is strictly related to a specific immunophenotype, namely ALL of T-cell lineage; (ii) no significant correlation exists between alterations at chromosome 9p level and the homozygous deletions of p16^INK4A gene; and (iii) p18 gene was not deleted in the examined cases. These findings suggest a possible correlation between the T-lymphocyte phenotype and the expression of p16^INK4A gene. Moreover, the absence of MTAPase activity seems to be a valuable marker of p16^INK4A gene inactivation, thus indicating that the deleted chromosomal area on 9p21 very frequently involves the MTAPase gene.     

Thyrotropin Releasing Hormone Analog TA-0910 Suppresses Alcohol Intake in Alcohol Drinking African Green Monkeys

In previous studies, we found that single injections of the thyrotropin-releasing hormone analog TA-0910 dose-dependently reduced alcohol intake and preference in alcohol-preferring (P) and Fawn-Hooded (FH) rats over a 24-hr period of continuous access to alcohol and water. However, several consecutive daily injections of TA-0910 resulted in the development of tolerance to these effects. In the present study, we found that in a 5-hr limited-access schedule in which monkeys could select an aqueous alcohol solution (7.5% v/v) or tap water, single doses of TA-0910 (0.0625, 0.125, 0.25, 0.5, and 0.75 mg/kg), similar to those found effective in P and FH rats, reduced consumption of alcohol. In this protocol, tolerance to the attenuating effects of TA-0910 on alcohol intake was not evident after five consecutive once-daily doses of 0.5 mg/kg. Furthermore, it was shown that a single dose of 0.75 mg/kg TA-0910 did not significantly influence 24-hr water intake when water was the only available fluid, but did reduce the intake of a preferred solution of saccharin. These findings suggest that activation of brain thyrotropin-releasing hormone systems reduces alcohol intake in primates and that tolerance to this effect is not evident within 5 days under a limited access schedule.     

Human GABA, Receptor αl and α3 Subunits Genes and Alcoholism

γ-Aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the brain. GABA effects are largely mediated by binding to the postsynaptic GABA_A receptor, causing the opening of an integral chloride-ion channel. The GABA_A antagonists picrotoxin and bicuculline reduce some ethanol-induced behaviors, such as motor impairment, sedation, and hypnosis. The role of this receptor in alcoholism is further supported by effective alleviation of alcohol withdrawal symptoms by GABA_A agonists. To determine the role of the GABA, receptor (GABR) genes in the development of alcoholism, we have used α₁ and α ₃ simple sequence repeat polymorphisms in a sample of unrelated alcoholics, alcoholic probands with both parents, and psychiatrically normal controls. For the GABRα₁ gene, the differences between allele frequencies, when all alleles were compared together, were not significant between total alcoholics, subtypes of alcoholics, and normal controls. However, for GABRα₃, the differences between total alcoholics and normal controls were significant when all alleles were compared together. The differences between subtypes of alcoholics and normal controls were not significant. The results of haplotype relative risk analysis for both genes, GABRα₁ and GABRα₃, were also negative. It is possible that the sample size in the haplotype relative risk is too small to have power to detect the differences in transmitted versus nontransmitted alleles. There is a need for a replication study in a large family sample, that will allow haplotype relative risk or affected sib-pair analysis.     

Effects of CRF1-receptor and opioid-receptor antagonists on dependence-induced increases in alcohol drinking by alcohol-preferring (P) rats

Background:  Selective breeding of rats over generations and induction of alcohol dependence via chronic vapor inhalation both enhance alcohol consumption in animal models. The purpose of this study was to determine whether dependence-induced increases in alcohol consumption by P rats is sensitive to naltrexone, a general opioid receptor antagonist (but with highest affinity at the μ-opioid receptor at low doses), and the recently characterized small molecule CRF₁-receptor antagonist MPZP ( N,N -bis(2-methoxyethyl)-3-(4-methoxy-2-methylphenyl)-2,5-dimethyl-pyrazolo[1,5- a ]pyrimidin-7-amine).
Methods:  P rats ( n  =   20) were trained to respond for alcohol and water in a 2-lever operant situation during daily 30-minute sessions. P rats were then matched for alcohol intake and exposed to chronic intermittent alcohol vapor ( n  =   10) or ambient air ( n  =   10) for approximately 10 weeks. All rats were then administered MPZP and naltrexone in 2 separate and consecutive Latin-square designs.
Results:  MPZP attenuated dependence-induced increases in alcohol intake by P rats while having no effect on alcohol consumption by nondependent controls. Conversely, operant alcohol responding was reduced similarly in dependent and nondependent P rats by naltrexone.
Conclusions:  These results confirm a role for brain CRF₁-receptor systems in dependence-induced changes in the reinforcing properties of alcohol, and CRF₁-receptor blockade appears to suppress dependence-induced drinking at lower doses in P rats relative to other rat lines. Therefore, brain CRF₁-receptor systems are important in the regulation of dependence-induced alcohol consumption, whereas brain opioid systems are important in the regulation of basal alcohol consumption by rats.     

Melatonin counteracts lipid peroxidation induced by carbon tetrachloride but does not restore glucose-6 phosphatase activity

Abstract: Carbon tetrachloride (CC1₄) exerts its toxic effects by the generation of free radicals. In this study we investigated whether melatonin, a potent free radical scavenger, could prevent the deleterious effects of CC1₄. Liver homogenates and liver microsomes were incubated with CCI4 in the presence of melatonin and lipid peroxidation and glucose-6 phosphatase (G6Pase) activity were determined. All doses of CC1₄ (1, 0.5, 0.1 raM) produced significantly high levels of lipid peroxidation, as reflected by increased levels of malonaldehyde and 4-hydroxyalkenals, in both liver homogenates and liver microsomes. These doses of CC1₄ concommitantly reduced the activity of microsomal G6Pase. Co-incubation with melatonin dose-dependently (2, 1, 0.5 raM) inhibited the production of lipid peroxidation, but it was unable to restore the activity of G6Pase. In in vivo studies, rats were also treated with melatonin (10 mg/kg, i.p.), given 30 min before and 60 min after the administration of CC1₄ (5 ml/kg, i.p.). Significantly elevated levels of lipid peroxidation were measured in the liver and kidney. Melatonin prevented the CCl₄-induced lipid peroxidation in the kidney, but not in the liver. These data suggest that melatonin may provide protection against some of the damaging effects of CCI4, possibly due to its ability to scavenge toxic free radicals.