Alcohol drinking in rats is attenuated by the mixed 5-HT1 agonist/5-HT2 antagonist FG 5893

A safety and tolerability laboratory study of the combination of aripiprazole and topiramate in volunteers who drink alcohol

OBJECTIVE

There are no reports examining the safety of taking both topiramate and aripiprazole together with alcohol. The ultimate aim for this research is to determine whether this combination is safe and is superior to either drug taken alone in reducing alcohol use in alcohol dependent patients.

METHOD

This was an open-label trial. Thirteen heavy drinking participants not seeking treatment for alcoholism were randomized. Participants were titrated up to 300 mg of topiramate and 30 mg of aripiprazole a day over 35 days. Participants reported adverse events (AEs) daily alcohol use and participated in an alcohol challenge session (ACS).

RESULTS

The eight participants who completed the study achieved the maximum doses of drugs. The AEs of the drugs would suggest that the AEs profile is broader but not additive. Alcohol use from the 28 days before screening to the seven days before the ACS was reduced (p = 0.08).

CONCLUSION

There was no evidence that AEs of aripiprazole and topiramate are additive and can, therefore, be administered safely together with a modest amount of alcohol. There was also a trend for a reduction of alcohol use by participants. This finding has implications for further investigation of this combination of drugs for alcohol dependence.

Aripiprazole in the treatment of patients with alcohol dependence: a double-blind, comparison trial vs. naltrexone

Substantial evidence suggests that both partial dopamine agents and mixed 5-HT1A/2A receptor drugs independently show significant efficacy in reducing alcohol use in both animals and humans. Aripiprazole, which acts as a dopamine/5-HT system stabilizer, approaches the optimal characteristics sought in medication to be considered for testing in the treatment of alcohol dependence. In this randomised, double-blind, confrontation trial with naltrexone, we aimed to investigate the efficacy of aripiprazole on alcohol-drinking indices. Craving and psychiatric symptom improvements were the secondary end points. Seventy-five alcohol dependent subjects were detoxified and were subsequently randomised into two groups, receiving 50 mg of naltrexone and 5-15 mg of aripiprazole, respectively. Craving (Visual Analogue Scale; Obsessive and Compulsive Drinking Scale) and withdrawal (Clinical Institute Withdrawal Assessment) rating scales were applied; psychiatric symptoms were evaluated through the Symptom Check List 90-Revised. The number of subjects remained alcohol free for the entire study period (16 weeks) and the number of subjects relapsed were not significantly different in the two groups. The survival function showed that patients treated with aripiprazole remained abstinent from any alcohol amount for a longer time with respect to those treated with naltrexone. As for craving scores, patients treated with naltrexone showed a better outcome. Results from this study globally place aripiprazole at the same range of efficacy of naltrexone, one of the approved drugs used in alcohol relapse prevention. If it could be demonstrated in placebo-controlled trials that aripiprazole is efficacious in decreasing alcohol use, lessening craving, and attenuating psychopathological symptom severity, we will have gained a powerful agent for the treatment of alcohol-dependent subjects.

Morphometry of dorsal raphe nucleus serotonergic neurons in alcoholism

BACKGROUND

Reduced serotonergic function is hypothesized in alcohol abuse and dependence. Serotonergic innervation of the cortex arises predominantly from the dorsal raphe nucleus (DRN). We sought to determine the number and morphometric characteristics of DRN serotonergic neurons postmortem in alcoholic individuals (n=9; age: 16-66 years; 8M:1F) compared with psychiatrically normal, nonalcoholic controls (n=6; age: 17-74 years; 4M:2F).

METHODS

Brainstems were collected at autopsy, fixed and cryoprotected. Alcohol dependence or abuse was determined by psychological autopsy (DSM-IV), the presence of liver fatty changes or cirrhosis and/or high blood alcohol level. Tissue was sectioned at 50 microm (-25 degrees C). A series of 1:10 sections was immunoreacted with antiserum to tryptophan hydroxylase (TPH), the rate-limiting enzyme in the biosynthesis of serotonin. The total number of TPH-immunoreactive (IR) DRN neurons was determined by stereology. Neuron morphometry indices were determined using a video-based imaging system attached to a microscope. We identified TPH-IR neurons every 1,000 microm in each brainstem and measured neuron area, total cross sectional neuron area, and the total area and density of immunolabeled processes.

RESULTS

Dorsal raphe nucleus neuron number (controls: 80,386+/-10,238; alcoholic individuals: 85,884+/-12,478) was not different between groups but TPH-IR was greater in alcoholic individuals throughout the rostrocaudal extent of the DRN. The volume of the DRN was 66+/-9 mm3 in controls and 55+/-5 mm3 in alcoholic individuals (p>0.05). The average size of DRN neurons did not differ between groups (353+/-12 microm2 for controls vs 360+/-15 microm2 for alcoholic subjects). However, the area occupied by neuron processes (area of processes/DRN area) was 2.2-fold greater in alcoholic individuals compared with controls (p<0.05).

CONCLUSIONS

The increased area occupied by neuron processes in alcoholic individuals may represent sprouting and, together with greater TPH-IR, be a compensatory response to impaired serotonergic transmission or cumulative effects of alcohol on the serotonin system.

The mixed 5-HT 1A/2A receptor drug FG5938 suppresses alcohol drinking while enhancing feeding in P rats

The neurotransmitter serotonin (5-HT) has long been implicated in the etiology of aberrant consumption of alcohol. Several compounds thought to possess a potential therapeutic value to counteract drinking have high affinities for 5-HT1A and 5-HT2A receptors in the brain. For example, amperozide and FG5865 significantly reduce the volitional intake of alcohol, without altering food intake, both in rats genetically predisposed or chemically induced to drink alcohol. The present study was undertaken in the alcohol-preferring (P) rat to determine whether an amperozide like drug. FG5938 (1-[4-(p-fluorophenyl)butyl]-4-(6-methyl-2-pyridinyl)-piperazine fumarate). exerts an action on the volitional drinking of alcohol as well as on the intakes of food and water. In 11 male P rats, the pattern of preference for different concentrations of alcohol was determined by an 11-day test for water vs. 3 to 30% alcohol solutions. After maximally preferred alcohol concentrations, i.e., 9 to 15% had stabilized for 4 days, saline or FG5938 was injected subcutaneously at 1600 and 2200 h in a dose of 2.5, 5.0, or 10.0 mg/kg over 4 consecutive days. Following treatment, preference testing for the same concentrations of alcohol was continued for 5 additional days. FG5938 caused a significant suppression in alcohol drinking in terms of both absolute g/kg and proportion to total fluid intake. During its administration, FG5938 also enhanced the ingestion of food and water of the P animals significantly, with the largest intake occurring on the initial day, while body weights increased. After FG5938 injections, food and water intakes returned to predrug levels. The saline control vehicle had no significant effect on the intakes of alcohol, food, or water of the P rats. Overall, these results show that FG5938 acts to attenuate alcohol preference while simultaneously increasing the ingestion of food paradoxically. To our knowledge, this is the first known drug to possess this unique property. Finally, these findings support the view that a compound having affinities to both 5-HT1A and 5-HT2A receptors may be useful as a therapeutic agent in the treatment of alcoholism.

Pharmacotherapies for alcohol problems: a review of research with focus on developments since 1991

Research on medications to treat alcohol problems has flourished in the last 5 years. Whereas before this time most projects focused on withdrawal agents, at least equal interest has now extended to drugs that may directly reduce urge to drink. The most promising medications in this regard are the opiate antagonists and acamprosate. Considerable attention has also been devoted to serotonergic agents. As aids to detoxification, pharmacologic agents that affect the multiple neural systems disrupted by acute alcohol withdrawal remain under active investigation. Significant progress is also being made in identifying medications to assist alcoholics suffering collateral psychopathology, especially depression and anxiety based disorders. Unfortunately, fewer gains have been realized in the development of medications to assist patients simultaneously dependent on both alcohol and illicit drugs. Also, research to develop amethystic agents remains in its very early stages.

Differential efficacy of serotonergic drugs FG5974, FG5893, and amperozide in reducing alcohol drinking in P rats

Amperozide (FG5606), a 5-HT2 receptor antagonist, is well known to suppress alcohol consumption in different rat models of drinking. The present study compared the efficacy of three drugs, FG5974, FG5893, and amperozide, which have differential affinities for 5-HT1A and 5-HT2A receptors, on alcohol drinking in the genetic alcohol-preferring (P) rat. After preference for alcohol vs. water was determined over 10 days when concentrations of alcohol were increased from 3% to 30%, the maximal concentration of alcohol preferred by each animal was selected for drug testing. A 4-day predrug preference test was followed by SC injection of the saline control vehicle or doses of 1.0 and 2.5 mg/kg FG5974, FG5893, or amperozide given at 1600 and 2200 h for 4 days. Alcohol preference testing concluded with a final 4-day interval. A total daily dose of 5.0 mg/kg FG5974 reduced absolute g/kg intake of alcohol and proportional intakes of the P rats significantly; the lower dose of FG5974 also reduced alcohol drinking significantly following treatment. The mixed 5-HT1A agonist/5-HT2A antagonist, FG5893, which suppresses drinking in cyanamide-treated rats, was without effect on alcohol ingested by the P rats. However, amperozide caused a dose-dependent decline in both absolute intakes and proportion of alcohol that was more intense than that of FG5974. The control vehicle failed to alter alcohol drinking and, like the FG compounds, did not affect food intake or body weight. Although the inhibition of alcohol drinking by amperozide corresponds precisely with previous findings, the effect of FG5974 contrasts to results obtained with a structurally analogous drug FG5893. Thus, the genetic strain of rat as well as the nature of the chemical characteristics of a 5-HT agonist/antagonist will determine the differential efficacy of a drug in influencing the volitional drinking of alcohol.

Opiate and 5-HT2A receptors in alcohol drinking: preference in HAD rats is inhibited by combination treatment with naltrexone and amperozide

Amperozide, a 5-HT2A receptor antagonist, and naltrexone, an opiate receptor antagonist, have been shown to suppress volitional drinking of alcohol in experimental animals. The present study examined the effects of the concurrent administration of both drugs on the volitional intake of alcohol in the selectively bred, high alcohol drinking (HAD) rat. Individual preferences for alcohol were determined by a standard 10-day test in which alcohol concentrations were increased from 3% to 30%. Following a 4-day predrug test during which water together with a maximally preferred concentration of 7% to 20% was offered to each HAD rat, amperozide and naltrexone were injected SC over a second 4-day period as follows: 1) amperozide at 1600 h and naltrexone at 2200 h; 2) the same drugs but in reversed temporal order; and 3) amperozide and naltrexone administered simultaneously at 1600 and 2200 h. Thereafter, alcohol preference testing continued for a third 4-day period. The alternate delivery of both drugs attenuated significantly the absolute g/kg and proportional intakes of alcohol in the HAD rats, whereas the saline vehicle was without effect. Although the simultaneous administration of naltrexone and amperozide produced an even greater decline in alcohol intake, without side effects on food and water intakes or on body weight, some residual drinking of alcohol persisted. Nevertheless, the results corroborate our previous findings on the suppression of alcohol drinking by antagonists of opiate and 5-HT2A receptors. Because amperozide and naltrexone together reduce the apparent reinforcing property of alcohol, the theory is supported that the addictive liability to alcohol is underpined by multiple receptor subtypes within the mesolimbic and other systems in the brain.

Prefrontal levels of 5-HIAA, but not dopamine, predict alcohol consumption in male Wistar rats following 6-OHDA lesions

To examine the effects of dopamine (DA) on alcohol consumption, male Wistar rats were subjected either to 6-OHDA lesions of the frontal cortex (MPFC) or to a sham lesion/no lesion. Following surgery, rats were trained to drink alcohol on a sucrose-fading paradigm over the course of 6 weeks, at the completion of which they consumed a solution of 3% sucrose/10% alcohol. Daily consumption of alcohol was computed for each rat. Animals were sacrificed and the MPFC, nucleus accumbens (NA), and ventral tegmentum (VTA) were removed. Levels of DA and its metabolites (i.e., HVA and DOPAC), norepinephrine (NE), and serotonin (5-HT) and its metabolite (i.e., 5-HIAA) were measured for each brain region using HPLC with electrochemical detection. Post hoc analyses were run examining the relationship of DA and its metabolites, 5-HT and its metabolite (5-HIAA), and norepinephrine (NE) in the MPFC, NA, and VTA with alcohol consumption. The 6-OHDA lesions depleted DA to 74.5% of control levels in the MPFC, but did not significantly affect alcohol consumption. Post hoc analyses found that the "high" alcohol consumption group had significantly reduced levels of MPFC 5-HIAA in comparison to the "low" consumption group, but that there was no relationship of 5-HIAA levels in the VTA or NA to alcohol consumption. These findings suggest that MPFC DA is not critically involved in the regulation of alcohol consumption. They further suggest that MPFC serotonergic systems may play an important role in the regulation of alcohol consumption, although future experimentation directly manipulating 5-HT systems in the MPFC will be required to fully assess these findings.

A relationship between increased voluntary alcohol preference and basal hypercorticosteronemia associated with an attenuated rise in corticosterone output during stress

Some of the multiple biological effects of stress include activation of a variety of neuroendocrine systems, resulting in enhanced secretion of many hormones, including corticosterone, as well as facilitation of drug-seeking behavior. Therefore, we have examined the potential relationship between voluntary alcohol consumption (VAC) and corticosterone output profile using: (1) selectively bred alcohol-preferring (P) and nonpreferring (NP) rats; and (2) outbred male Holtzman Sprague-Dawley rats selected for (a) low basal corticosterone (< 2 micrograms/mg Cr) and high stimulation (> 250%) (L-H rats), and (b) high basal corticosterone (> 4 micrograms/mg Cr) and low stimulation of corticosterone output on 24-hour fasting stress (< 125%) (H-L rats). The results of this study show: (a) the corticosterone output profiles of P and NP rats were similar to those of H-L and L-H rats, respectively; and (b) the H-L rats exhibited significantly higher VAC than the L-H rats. In conclusion, these data suggest that basal hypercorticosteronemia associated with attenuated rise in corticosterone output during stress may be associated with increased VAC.

New drugs for the treatment of experimental alcoholism

This article presents a current overview of the efforts to suppress pharmacologically the craving, dependence, or other factors associated with the self-selection of alcohol in an experimental animal. The contemporary status of the pharmacotherapy of experimental alcoholism similarly is described for different animal models of alcohol drinking. An evaluation is presented of several classes of drug for their efficacy in ameliorating the volitional ingestion of alcohol in the presence of an alternative fluid. Currently, two main experimental animal models of alcoholism are being used in this endeavor: (a) genetic lines or substrains of high alcohol preferring or high drinking rats; and (b) strains of nondrinking or low alcohol preferring rats which are induced chemically to prefer alcohol. Because of technical, methodological, and other issues surrounding the procedures used to assess the efficacy of a drug in reducing alcohol intake, several of the newer findings remain controversial. For example, serious side effects on the intake of food, caloric regulation, motor activity, or other functions would preclude the clinical utility of the drug. However, several drugs which affect monoaminergic neurons as well as opioid systems in the brain now seem to offer promise as agents which do possess clinical benefits. Two of these drugs, FG5606 (amperozide) and FG 5893 are essentially "antialcoholic" or anticraving and are without any significant side effects on cerebral mechanisms responsible for hunger, caloric intake, motor activity, or other physiological process. Amperozide, a 5-HT2 receptor antagonist with dopamine releasing properties, is particularly notable because of its irreversible nature in attenuating alcohol preference for months after its administration. It is concluded that future pharmacological research on presently available and newly developed compounds will provide exciting opportunities to the clinician who can utilize a particular drug as an adjunctive tool in the therapeutic treatment of the alcoholic individual.

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.

5-HT1A autoreceptor-mediated effects of the amperozide congeners, FG5865 and FG5893, on rat brain 5-hydroxytryptamine neurochemistry in vivo

The two diphenylbutylpiperazinepyridinyl derivatives, FG5865 and FG5893, have a unique receptor binding profile in that they show very high and essentially equipotent affinities for both 5-HT1A and 5-HT2 receptors. The present report describes the acute effects of FG5865 and FG5893 on presynaptic 5-hydroxytryptamine (5-HT) neuronal function in the rat CNS, using established ex vivo and in vivo neurochemical techniques. Post-mortem measurements of tissue levels of 5-HT, its metabolite, 5-hydroxyindoleacetic acid (5-HIAA), and of the formation of 5-hydroxytryptophan (5-HTP; after inhibition of aromatic amino acid decarboxylase by NSD 1015) showed that FG5865 (0.1-20 mg/kg, s.c.) and FG5893 (0.1-20 mg/kg, s.c.) dose dependently decreased the synthesis and the metabolism/turnover of 5-HT--this to an extent comparable to the reference 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin. Reserpine (5 mg/kg, s.c.) pretreatment did not prevent the FG5893-induced decrease of 5-HT synthesis rate. In contrast, about 25-50 times higher doses of FG5865 were required to produce a comparable decrease in brain 5-HT synthesis in reserpinized vs. non-pretreated rats. In in vivo microdialysis experiments, both FG5865 (0.1-3.0 mg/kg, s.c.) and FG5893 (0.03-1.0 mg/kg, s.c.) caused a marked and dose-dependent decrease of 5-HT release in the ventral hippocampus. Pretreatment with the 5-HT1A receptor antagonist, (+/-)-pindolol (8 mg/kg, s.c.), abolished the FG5865 (0.3 mg/kg, s.c.)-induced reduction of 5-HT release, and (-)-pindolol (8 mg/kg, s.c.) similarly reversed the FG5893 (0.3 mg/kg, s.c.)-induced decrease. Local infusion of FG5865 into the ventral hippocampus (10 microM, 20-min pulse) resulted in a rapid and transient elevation of the 5-HT output, an effect that was independent of extracellular Ca2+. FG5893, on the other hand, did not affect the 5-HT release upon local administration. The results demonstrate that FG5865 and FG5893 potently affect a range of neurochemical indices of rat brain 5-HT neuronal activity in vivo, in a way consistent with indirect (FG5865) and direct (FG5865 and FG5893) stimulation of the 5-HT1A autoreceptors in the raphe nuclei.

Failure of the 5-HT2 receptor antagonist, ritanserin, to alter preference for alcohol in drinking rats

The purpose of this study was to determine whether the 5-HT2 receptor antagonist, ritanserin, possesses the same sort of efficacy as another central 5-HT2 antagonist, amperozide, in reducing the pharmacologically induced preference for ethyl alcohol in the rat. Following the repeated administration of the inhibitor of aldehyde dehydrogenase, cyanamide, the preference for alcohol vs. water was determined in each of 20 Sprague-Dawley rats by a standard test using 3-30% concentrations. Then, each rat was offered water and its maximally preferred concentration of alcohol, which ranged from 9-15% and was consumed at a mean of 5.02 +/- 0.44 g/kg per day. After a 4-day predrug control test, either the saline control solution or 0.1, 0.3, or 1.0 mg/kg ritanserin was administered SC at 1600 h over 3 days. The daily intakes of alcohol of rats both during and after treatment with ritanserin were unchanged in terms of absolute g/kg and proportion of alcohol to total fluid consumed. Similarly, the control saline also was without any effect on alcohol consumption. Neither the consumption of food and total fluids nor the level of body weight was affected by these doses of ritanserin. Because our findings fail to coincide with previous reports on the effect of ritanserin on alcohol preference, it is envisaged that a methodological difference in earlier experimental procedures, such as the use of a weak 3% concentration of alcohol, could explain the discrepancy. Further, the present results contrast with the prolonged reduction in drinking produced by another 5-HT2 receptor antagonist, amperozide, which also acts centrally on dopaminergic neurons in the limbic system.(ABSTRACT TRUNCATED AT 250 WORDS)