New drugs for the treatment of experimental alcoholism

Warsaw high-preferring (WHP) and Warsaw low-preferring (WLP) lines of rats selectively bred for high and low voluntary ethanol intake: preliminary phenotypic characterization

The Warsaw High Preferring (WHP) and Warsaw Low Preferring (WLP) lines were bred from Wistar foundation stock to obtain lines of rats that differ in their preference for ethanol solutions. The WHP line has met several major criteria for an animal model of alcoholism. The WHP rats voluntarily drink excessive amounts of ethanol while the WLP rats consume negligible amounts of ethanol. The WHP rats attain physiologically active blood ethanol concentrations with chronic free-choice drinking. They also develop subtle but visible signs of physical dependence (the withdrawal signs). The patterns of ethanol consumption in WHP and WLP lines are stable in time and independent of the manner of access to ethanol solutions. Notably, when exposed to the increasing ethanol concentrations WHP rats gradually increased total ethanol intake whereas the WLP rats consumed invariably very low amounts of ethanol. Furthermore, the WHP rats show an increased responsiveness to the stimulatory effects of low dose of ethanol.

Maternal ethanol administration inhibits 5-hydroxytryptamine synthesis and tryptophan hydroxylase expression in the dorsal raphe of rat offspring

Maternal ethanol consumption during pregnancy has a detrimental effect on the central nervous system (CNS) development of fetus. 5-Hydroxytryptamine (5-HT) is an important neurotransmitter and/or neuromodulator in the mammalian CNS. Tryptophan hydroxylase (TPH) is the rate limiting enzyme of 5-HT synthesis. Ethanol is known to induce neuropsychiatric disorders by alteration of the central serotonergic system. In the present study, the effects of maternal ethanol intake on the 5-HT synthesis and the TPH expression in the dorsal raphe of rat offspring were investigated. The present results show that the synthesis of 5-HT and the expression of TPH in the dorsal raphe of rat offspring were suppressed by maternal ethanol intake and that the suppressive effect of alcohol was more potent in the 5 weeks old rat pups compared to the 3 weeks old rat pups. Based on the present study, it can be suggested that the pathogenesis of ethanol-induced neuropsychological disorders involves ethanol-induced suppression on the 5-HT synthesis and the TPH expression in the dorsal raphe of offspring.

Clozapine reduces alcohol drinking in Syrian golden hamsters

Alcohol abuse contributes substantially to the overall morbidity of schizophrenia. While typical antipsychotic medications do not limit alcohol use in patients with schizophrenia, emerging data suggest that the atypical antipsychotic clozapine does. To further elucidate the effects of these antipsychotics on alcohol use, we initiated a study in alcohol-preferring rodents. Syrian golden hamsters were given free-choice, unlimited access to alcohol. Nine days of treatment (s.c. injection) with clozapine (2-4 mg/kg/day), but not haloperidol (0.2-0.4 mg/kg/day), reduced alcohol drinking. Clozapine reduced alcohol drinking by 88% (from 11.3+/-1.7 to 1.4+/-0.2 g/kg/day) while increasing both water and food intake. Alcohol drinking gradually (during 24 days) returned toward baseline in the clozapine-treated animals when vehicle was substituted for clozapine. Further increasing the doses of haloperidol (0.6-1.0 mg/kg/day) had no effect on alcohol drinking; moreover, very low doses of haloperidol (0.025-0.1 mg/kg/day) tested in separate groups of hamsters also had no effect on alcohol drinking. This study demonstrates that clozapine, but not haloperidol, can effectively and reversibly decrease alcohol consumption in alcohol-preferring hamsters. The results are compatible with the observations that clozapine, but not haloperidol, limits alcohol use in patients with schizophrenia. These data further suggest that clozapine may serve as a prototype for developing novel treatments for alcohol abuse.

Role of protein kinase C in estrogen protection against apoptotic cerebellar cell death in ethanol-withdrawn rats

Results of studies from our laboratory have shown that administration of 17beta-estradiol (E(2)) reduces cerebellar neuronal damage during ethanol withdrawal (EW). In the current study, we examined mechanisms underlying E(2) protection against EW-associated cerebellar damage by assessing apoptotic indicators: DNA fragmentation, caspase-3 activity, and protein kinase C (PKC) activity. Ovariectomized rats, implanted with E(2) or oil pellets, received ethanol [7.5% weight/volume (wt./vol.)] (EW/E(2) group and EW/Oil group, respectively) chronically (for 5 weeks) or control dextrin diet (Dextrin/Oil group). At day 14 of EW, cerebelli were collected for the terminal deoxynucleotidyltransferase (TdT)-mediated dUDP-biotin nick end labeling (TUNEL) assay to detect DNA fragmentation and for immunohistochemistry to detect caspase-3 activation. A separate group of rat cerebelli was prepared to assess for total PKC activity, as well as for activity of a specific PKC isozyme, epsilon (PKCepsilon), by using an in vitro [gamma-(32)P]ATP phosphorylation assay at days 1 and 14 of EW. Results indicated that rats in the EW/Oil group had more DNA fragments and caspase-3-positive neuronal cells than observed for control rats, and these effects were inhibited by E(2) treatment. For total PKC activity at day 1 of EW, rats in the EW/E(2) group had a lower cytosolic PKC activity than observed for either rats in the EW/Oil group or control rats. At day 14 of EW, both EW groups had a lower total PKC activity than observed for control rats. For PKCepsilon activity, rats in the EW/E(2) group had a lower cytosolic PKCepsilon activity than observed for rats in the EW/Oil group or for control rats at day 1, and they had a lower membrane PKCepsilon activity at day 14 of EW than observed for control rats. These findings support the suggestion that E(2) protects against cerebellar neuronal damage in ethanol-withdrawn rats by inhibition of DNA fragmentation and caspase-3 activation, and that reduced PKC activity may be involved in the protection.

Role of the GABAA system in behavioral, motoric, and cerebellar protection by estrogen during ethanol withdrawal

Results of studies from our laboratory have shown that administration of 17beta-estradiol (E(2)) reduces cerebellar neuronal damage during ethanol withdrawal (EW). In the current study, we investigated whether the GABAergic system is involved in the protective effects of E(2) against the EW syndrome. To test this hypothesis, we examined the effects of GABAergic drugs, with and without E(2), on EW sign scores, motoric capacity, and caspase activation. Ovariectomized rats implanted with an E(2) or an oil pellet received liquid ethanol [7.5% weight/volume (wt./vol.)] for 5 weeks or dextrin diet, followed by 2 weeks of EW. A gamma-aminobutyric acid type A (GABA(A)) agonist, muscimol (0.125 or 0.25 mg/kg), and antagonist, bicuculline (1.25 mg/kg), were administered (intraperitoneally; three times a day for 4 days) starting 1 day before the onset of EW. On termination of chronic administration of ethanol diet, rats were tested for overt withdrawal signs and latency to fall from a rotarod. The initial latency was measured separately to assess motoric capacity before learning occurred. Cerebelli were subsequently collected for immunohistochemistry to detect caspase activation. Results showed that treatment with E(2) lowered EW sign scores and improved initial as well as subsequent rotarod latencies compared with findings without treatment with E(2) (control group). These effects of E(2) were enhanced by combined treatment with muscimol and diminished by bicuculline. Results also showed that ethanol-withdrawn rats had more caspase-3-positive cells than observed for the dextrin diet-fed group in a manner reversed by E(2) and exacerbated by bicuculline. Bicuculline also caused partial antagonism of the protective effect of E(2). These findings support the suggestion that GABA(A) agonists ameliorate, and GABA(A) antagonists exacerbate, EW signs, cerebellar neuronal damage, and motoric impairment in ethanol-withdrawn rats. Also, results of the current study provide indirect evidence that the GABAergic system is involved in protective effects of E(2) against the EW syndrome.

Estradiol protects against cerebellar damage and motor deficit in ethanol-withdrawn rats

On the basis of findings obtained from this study, we hypothesize that the female sex steroid 17beta-estradiol (E(2)) protects against cerebellar neuronal damage and behavioral deficit in rats withdrawn from chronic ethanol exposure. Ovariectomized rats implanted with E(2) or an oil pellet received liquid ethanol (7.5% [wt./vol.]) or dextrin diet for 5 weeks, followed by 2 weeks of ethanol withdrawal. On termination of diet administration, rats were tested for both overt withdrawal signs and latency (seconds) to fall from an accelerating rotarod in six consecutive sessions (the longer the latency, the better the performance). The initial latency was measured separately to assess motoric capacity before learning occurred. Rats were then killed, and cerebella were prepared for accessing of Purkinje cell damage. The study revealed three specific findings. (1) In the absence of E(2), the ethanol withdrawal group showed higher total ethanol withdrawal sign scores than those for the dextrin group, whereas the score for the ethanol withdrawal group was lower in the presence of E(2). (2) In the absence of E(2), the ethanol withdrawal group showed shorter rotarod latency than that for the dextrin group, whereas the latency for the ethanol withdrawal group increased in the E(2)-treated group. In ethanol withdrawal groups, E(2) treatment also resulted in a longer latency than that observed with oil treatment in the initial session and in subsequent sessions. (3) Purkinje cell numbers in the ethanol withdrawal group without E(2) were lower than those in dextrin groups and in the ethanol withdrawal group with E(2) treatment. These findings support the suggestion that E(2) exerts protective effects against withdrawal signs, cerebellar neuronal damage, and motoric impairment in subjects exposed to, and withdrawn from, chronic ethanol exposure.

Opiate delta-2-receptor antagonist naltriben does not alter discriminative stimulus effects of ethanol

The ability of a selective 2-opiate receptor antagonist, naltriben, to modulate ethanol discrimination was investigated in a rat model using a drug discrimination procedure. Rats were trained to discriminate ethanol (1.25 g/kg, IP) from saline on a fixed-ratio schedule, FR10. Once rats had acquired the ethanol-saline discrimination, ethanol dose-response tests were conducted with 15-min pretest injections. Following the characterization of the ethanol dose-response curve, the effect of naltriben on ethanol's discriminative stimulus was assessed by administering naltriben (0. 032-5.6 mg/kg, IP) 15 min before the ethanol administration. In the present study, naltriben did not have any modulatory effect on ethanol discrimination, suggesting that either Delta(2)-opiate receptors are not involved in the formation of ethanol's discriminative stimulus or the antagonism of Delta(2)-opiate receptors is not sufficient to alter ethanol's compound discriminative stimulus.

Association study between genetic polymorphisms in the 14-3-3 eta chain and dopamine D4 receptor genes and alcoholism

BACKGROUND

The dopaminergic system may be involved in the development of alcoholism. As part of our ongoing studies on the association between alcoholism and dopaminergic genes, we report herein a mutation analysis of the 14-3-3 eta chain gene (YWHAH) and an association study between alcoholism and the YWHAH and dopamine D4 receptor gene (DRD4) polymorphisms.

METHODS

Nucleotide mutations were investigated using single-strand conformation polymorphism methods. Associations were analyzed using a case-control design involving 185 Japanese alcoholics and 286 Japanese controls.

RESULTS

Five polymorphisms, -147G>A, -134(GCCTGCA)2-4, IVS1+31(G)7-8, IVS1+73-74ins(G), and 753A>G, were detected on the YWHAH, and three of them were novel. No significant associations were found between alcoholism and these polymorphisms or two additional polymorphisms on DRD4 exon III and DRD4 -521C/T.

CONCLUSIONS

YWHAH and DRD4 do not appear to play a major role in the development of alcoholism.

Effects of chronic ethanol administration on serotonin metabolism in the various regions of the rat brain

Changes in serotonin (5-HT) and 5-hydroxy indole acetic acid (5-HIAA), its major metabolite, in cerebral cortex, corpus striatum and hippocampus were investigated at 10th and 21st days of chronic ethanol ingestion in Wistar rats. Ethanol (7.2% v/v) was given to rats in a modified liquid diet. Biochemical analysis was performed in two groups of ethanol-treated and control rats (n = 6 for each group). Rats in each group were decapitated at the 10th and 21st days of ethanol consumption. Brains were removed and cerebral cortex, corpus striatum and hippocampus were dissected. 5-HT and 5-HIAA levels were measured in respective brain regions by using high performance liquid chromatography. In cerebral cortex and corpus striatum, 5-HT levels were significantly lower than control at the 10th day of ethanol consumption. At the 21st day, the levels tended to remain low, but not significantly different statistically. In hippocampus, 5-HIAA levels were significantly higher than control at 10th day of ethanol consumption. Increased 5-HIAA level returned to control values at the 21 st day of ethanol consumption. Our results suggest that, 5-HT clearly seems to play a critical role in the brain at the 10th day of chronic ethanol consumption.

Genome polymorphism and alcoholism

Different gene variants have been identified as risk or protective factors in alcoholism. The genes coding for dopamine receptors, serotonin transporters, and dehydrogenases represent susceptibility loci for addictive behaviour. However, alcoholism represents a complex psychiatric symptomatology which is caused by multiple factors, both genetic and environmental. Furthermore, there are probably different subtypes of alcoholism each with a distinct pathophysiology, and thus a different genetic background. Genetic research can help to identify such subtypes, which may require different therapeutic approaches. However, gene polymorphisms are not only responsible for a predisposition to alcoholism, but also for personality traits which influence the likelihood of developing addictive behaviour. Moreover, genetic polymorphisms are probably involved in the way an individual responds to treatment. Also, the severity of secondary diseases resulting from chronic alcohol uptake may depend on the genetic makeup of an individual. New treatment strategies focusing on genes contributing towards drug and alcohol dependence (such as gene therapy) are already under examination in animal models. However, further research is required before these developments will considerably change today's clinical handling of alcoholism.

The role of drug-paired stimuli in extinction and reinstatement of ethanol-seeking behaviour in the rat

Male Wistar rats were trained to respond for ethanol (30 min/day) in an oral self-administration procedure. A single lever press resulted in presentation of 0.1 ml of 8% ethanol from a liquid dipper. When responding for ethanol stabilised, reinstatement sessions started. In the 30-min reinstatement session, lever pressing was first extinguished for 20 min by switching the dipper off. Then, different kinds of stimuli were non-contingently delivered and reinstatement of lever pressing was assessed. Fifteen random (random time = 15 s) presentations of the dipper containing 8% ethanol potently reinstated ethanol-seeking. The reinstatement of lever pressing was immediate and most responses were emitted during the time needed for the first five presentations to occur. Presentations of the empty dipper or delivery of a non-specific stimulus (high-amplitude tone) did not produce any reinstatement. These results indicate that non-contingent presentations of the ethanol-associated stimulus complex may reinstate operant behaviour previously reinforced with ethanol.

Discriminative stimulus effects of ethanol: neuropharmacological characterization

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

Interaction of CCK and 8-OH-DPAT in the satiation of alcohol intake

Administration of the neuropeptide cholecystokinin (CCK) is known to reduce food and alcohol intake and preference. The food satiation effect of CCK is reportedly dependent on serotonergic neurotransmission. Administration of 8-OH-DPAT, a serotonin1A autoreceptor agonist, reduces the ability of CCK to inhibit feeding. We determined if CCK's alcohol satiation effect also depends on activity of serotonergic neurons by administering 8-OH-DPAT (120-240 microg/kg) to 23-h water-deprived female and male rats, followed 1 h later by i.p. injection of CCK (4 microg/kg) and 30-min access to 5% w/v ethanol. 8-OH-DPAT significantly (p < 0.05) interacted with CCK, and reduced CCK's ethanol satiation effect when given i.p. but increased CCK's effect when given s.c. Female rats showed this interaction of 8-OH-DPAT with CCK at a higher dose than males when given i.p., but females were more sensitive to s.c. 8-OH-DPAT's ability to reduce ethanol intake. Results are consistent with previous findings of dose-, sex-, and route-dependent biphasic effects of 8-OH-DPAT on feeding and ethanol intake. A partial dependence of CCK's alcohol satiation effect on serotonergic neurotransmission is revealed in this design.

Citalopram as an inhibitor of voluntary ethanol intake in the male rat

Psychological dependence was induced in rats by a 1-year intermittent exposure to intoxicating doses of ethanol, and recorded by the rat's ability to later take the same dose of ethanol independent of the offered concentration. Citalopram (10 or 40 mg/kg/day) was given for 3 weeks with ethanol available only the first and the last day; 10 mg/kg had no effect. On the first treatment day 40 mg/kg decreased ethanol intake. On the last treatment day 40 mg/kg had no effect. The following week the ethanol intake was higher than before the treatment in the 40 mg/kg group. During the four posttreatment weeks the ethanol intake of the 40 mg/kg group dropped significantly. Citalopram was retested 18 weeks after the first treatment during 1 week, with continuous access to ethanol; 10 mg/kg had no effect and 40 mg/kg decreased ethanol intake at day 1, reaching a minimum in day 3. A tolerance to this effect was seen at the end of the week. Thus, in this model an acute dose of citalopram can decrease ethanol intake, but tolerance to this effect develops when citalopram is given both with and without access to ethanol.

Pharmacological treatment of alcoholism

1. Pharmacological treatments are effective as part of a treatment plan that includes substantial education, psychological therapy and social support. This paper reviews recent literature on animal models of and treatment for alcohol abuse under seven categories: agents to block craving or reduce alcohol intake, agents to induce aversion to alcohol, agents to treat acute alcohol withdrawal, agents to treat protracted alcohol withdrawal, agents to diminish drinking by treating associated psychiatric pathology, agents to decrease drinking by treating associated drug abuse, and agents to induce sobriety in intoxicated individuals. 2. The benzodiazepines provide safe and effective treatment for detoxification, although current research focuses on finding drugs with a smaller likelihood of dependence. As yet, there are no drugs that effectively reverse the intoxicating effects of alcohol. 3. Currently, only two major groups of drugs that are relatively safe have shown any effect at reducing alcohol consumption: aversives such as disulfiram, and opioid antagonists such as naltrexone. 4. Finally, it is important to customize therapy for each patient rather than putting everyone through a standard treatment plan, especially in regards to the use of antidepressant or antipsychotic medications. Tailoring the program to the patient's needs dramatically improves the outcome of therapy and reduces the risk of adverse effects.

Drinking patterns in genetic low-alcohol-drinking (LAD) rats after systemic cyanamide and cerebral injections of THP or 6-OHDA

A key question related to the role of acetaldehyde and aldehyde adducts in alcoholism concerns their relationship to the genetic mechanisms underlying drinking. Experimentally, the low-alcohol-drinking (LAD) rat represents a standard rodent model having a strong aversion to alcohol. In these experiments, preferences for water vs. alcohol, offered in concentrations from 3% to 30%, were determined over 10 days in adult LAD rats (N = 6 per group). Then a saline vehicle or either 10 or 20 mg/kg of the aldehyde dehydrogenase (AIDH) inhibitor, cyanamide, was injected s.c. twice daily for 3 days. Secondly, either 0.5 or 1.0 microg of tetrahydropapaveroline (THP) was infused i.c.v. twice daily for 3 days in LAD rats (N = 8) and, as a genetic control, THP also was infused identically in Sprague-Dawley (SD) rats (N = 8). The results showed that the lower and higher doses of cyanamide augmented alcohol intakes in 33% and 50% of the LAD rats, respectively, with the patterns of drinking resembling that of genetic high-alcohol-drinking HAD or P rats. Although i.c.v. infusions of THP had little effect on alcohol preference of LAD rats, alcohol drinking was enhanced significantly in the SD rats. In a supplementary study, 200 microg of 6-hydroxydopamine (6-OHDA) also was infused i.c.v. in LAD rats (N = 7) on two consecutive days; no change occurred in the characteristic aversion to alcohol. These findings suggest that in certain individuals, a perturbation in the synthesis of AIDH can modify the genetically based aversion to alcohol, thus precipitating the liability for alcoholism. In that neither THP nor 6-OHDA lesioning exerted any effect on the genetic nondrinking LAD animal suggests that an unknown endogenous factor in the brain must underlie the cyanamide-induced shift to alcohol preference. We conclude that the genetic elements that normally prevent the progression to addictive drinking in most individuals appear to be invariant and irreversible.

Nefazodone attenuates the behavioral and neurochemical effects of ethanol

This study evaluated the influence of nefazodone, a combined 5-HT2A receptor antagonist and 5-HT reuptake inhibitor, on the behavioral and neurochemical effects of ethanol in nonselected male Wistar rats. In microdialysis experiments, ethanol (2.5 g/kg, i.p.) increased extracellular accumbal dopamine levels by 36% (p = 0.0073) compared to baseline levels, and elevated the maximal DOPAC and HVA levels by 26% (p = 0.0093) and 52% (p = 0.0010), respectively, Nefazodone (50 mg/kg, s.c.) per se increased accumbal dopamine levels by 28% (p = 0.0199) but, when injected 40 min before ethanol, reduced the ethanol-induced elevation of accumbal dopamine overflow (p = 0.0132) and decreased the ethanol-induced HVA levels (p = 0.0159). In an ethanol(6% v/v)/water free-choice paradigm, nefazodone (50 mg/kg, s.c.) decreased ethanol intake by 51% (p = 0.0251) and preference by 22% (p = 0.0251) in high- but not low-preferring rats from a nonselected Wistar strain. These results show that nefazodone modulates the mesolimbic dopamine system in a dopamine activity-dependent manner, and influences the neurochemical and behavioral effects of ethanol in the rat.

Psychopharmacotherapy for addictive and comorbid disorders: current studies

Proper diagnosis of comorbid disorders is crucial in treatment planning for the dually diagnosed. Since psychoactive substance use can obfuscate the diagnosis, special care must be taken to exclude organically based syndromes. Adequate periods of abstinence should first be achieved and subsequently the patient re-examined for residual symptoms compatible with a nonaddictive, nonsubstance-induced psychiatric disorder. The integration of concurrent treatment of both the mental and the addictive disorders appears to be the best approach for treatment of comorbid psychiatric and addictive disorders. An abstinence-based model that typically utilizes a 12-step group therapy is often employed for the addictive illnesses. Other forms of psychosocial therapies such as case managers are being used as well. Presently, physicians' prescribing practices for comorbid addicted patients are based on traditional approaches to use of medications in psychiatric patients, and their attitudes towards addictive disorders may play a significant role in determining the overall success of treatment.

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

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

The 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.

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.

Effects of nimodipine and other calcium channel antagonists in alcohol-preferring AA rats

Several lines of evidence suggest that L-type calcium (CA2+) channels play a role in excessive ethanol (EtOH) intake. In accordance with this, a considerable amount of antagonists for these ion channels has been found to suppress EtOH intake and preference in various animal models of alcoholism. The aim of the present study was to examine antialcohol effects of L-type Ca2+ channel antagonists in alcohol-preferring AA rats. These rats, a Wistar line selectively bred for a high 10% v/v EtOH preference in a free-choice situation, have thus far not been subjected to systematic investigations with Ca2+ channel antagonists. Therefore, effects on EtOH preference and intake, as well as on food and total fluid intake, were evaluated for the 1,4-dihydropyridine (DHP) derivatives nimodipine, felodipine, isradipine, nicardipine, nifedipine, and nitrendipine, as well as for the phenylalkylamine verapamil and the benzothiazepine diltiazem, utilizing a limited access, free-choice procedure. All DHPs were found to be highly effective in reducing both EtOH intake and preference, without affecting total fluid intake. Irrespective of route of application (IP or PO), the effective dose ranges were found to be very similar across compounds (10-30 mg/kg). Nevertheless, because food intake was also reduced, the effects were not completely selective. For nimodipine, the (-)-enantiomer seemed to be more effective as its (+)-enantiomer, possibly reflecting stereoselectivity at central binding sites. Compared to the DHPs, verapamil produced a similar profile of activity, but diltiazem was found to be ineffective. These results confirm and extend previous findings with L-type Ca2+ channel antagonists obtained in other models of alcoholism and suggest that this class of compounds offers an interesting approach for the pharmacotherapy of alcoholism.

Lesioning of midbrain raphe nuclei with 5,7-DHT fails to alter ethanol intake in the low alcohol drinking (LAD) rat

1. The effect of 10 g 5,7-dihydroxytryptamine (5,7-DHT) micro-injected into both the dorsal (DRN) and the median raphe nuclei (MRN) on the intake of ethanol in the low alcohol drinking (LAD) rat was measured using a standard 3-30% ethanol preference test. 2. The combined lesion of both midbrain structures depleted the levels of serotonin (5-HT) and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) significantly in each of eight major regions of the brain. The levels of norepinephrine, dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) remained unchanged after the lesion. 3. The effects of the neurotoxin lesions on the intakes of ethanol, food, water and total amount of fluid consumed were not significant. 4. The results corroborate our previous findings with the Sprague-Dawley strain of rat and suggest that although brain 5-HT may play a role in the maintenance of basal patterns of ethanol drinking, this monoamine may not be able to modify further the consumption of this fluid after lesioning with 5,7-DHT.

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.

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

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

Synthesis of dopamine and 5-HT in anatomical regions of the rat's brain is unaffected by sustained infusion of amperozide

The 5-HT2A antagonist, amperozide, is considered to be a potentially useful drug for the treatment of substance abuse. The effects of this drug on the Sprague-Dawley rat were examined on the synthesis of dopamine and serotonin (5-HT) as well as on the intakes of food and water and the level of body weight. Amperozide was delivered subcutaneously by osmotic minipump in doses of 2.5 mg/kg or 5.0 mg/kg per day for 7 days. After injection of 100 mg/kg NSD-1015, each brain was dissected post mortem into midbrain, pons, hypothalamus, septum, nucleus accumbens, striatum, frontal cortex and the hippocampus. Neither concentration of amperozide altered the synthesis of dopamine or 5-HT, as measured in terms of the formation of 1-3,4-dihydroxyphenylalanine (L-DOPA) and 5-hydroxytryptophan (5-HTP), respectively, in any of the 8 brain regions analyzed. Both doses of amperozide reduced food intake by 20% within 24 hr after implantation of the pumps, but feeding resumed postoperatively at the control level within 48 hr. Amperozide affected neither the intake of water nor the level of body weight. The lack of effect on the synthesis of dopamine and 5-HT and the absence of side effects on the intakes of food and water suggest that amperozide may be a specific agent for suppressing alcohol drinking.

Tomato juice, chocolate drink, and other fluids suppress volitional drinking of alcohol in the female Syrian golden hamster

Although the hamster generally prefers alcohol at a level similar to that of the rat or mouse selectively bred to consume alcohol, the drinking hamster demonstrates neither physical dependence on alcohol nor elevated blood levels of alcohol, which are two typical criteria characterizing an animal model of alcoholism. The present investigation was designed to determine whether a third criterion of an animal model (i.e., consumption of high levels of alcohol in the presence of a palatable fluid, fulfilled by the P rat) would be met by the female Syrian golden hamster (Mesocricetus auratus). A standard 3-bottle preference test was undertaken in 6 female hamsters over an 11 day period, in which water was presented in one tube and, in a second tube, a v/v solution of alcohol which was increased in concentration from 3% to 50% on each day as follows: 3%, 5%, 7%, 9%, 12%, 15%, 20%, 25%, 30%, 40%, and 50%. Then each hamster was offered its individually determined, maximally preferred concentration of alcohol for 4-8 days, which was 20%, 25%, or 30% alcohol. The mean absolute intake of alcohol during this period was 17.9 +/- 1.1 g/kg per day, whereas the mean proportion of alcohol to total fluid was 0.68 +/- 0.05. Then over a 4-day interval, a solution of tomato juice, peach juice, mango juice, dextrose and a chocolate beverage (Ensure Plus), all made isocaloric to the alcohol solutions with dextrose, was placed in the third tube simultaneously with water and the individually preferred concentration of alcohol.(ABSTRACT TRUNCATED AT 250 WORDS)

Female Syrian golden hamster: drinking of high concentrations of ethanol aversive to other mammals

The present experiments were designed to determine: 1) the pattern of preference for different concentrations of ethanol in the female Syrian golden hamster (Mesocricetus auratus), and 2) the influence of drinking ethanol on their intakes of food and total calories. A standard three-bottle preference test was undertaken in six female hamsters over an 11-day period in which water was offered together with ethanol, which was increased in concentration over 11 days from 3% to 50% as follows: 3%, 5%, 7%, 9%, 12%, 15%, 20%, 25%, 30%, 40%, 50%. Then, each hamster was offered its individually preferred concentration for a period of 8 days until the intake of ethanol had stabilized. During the preference testing for 3-25% solutions, the proportional intakes ranged between 0.6 and 0.8 whereas the mean absolute amount consumed per day increased from 2.3 to 16.1 g/kg at the 25% concentration. However, at the 50% concentration, ethanol drinking declined substantially to 8.7 g/kg per day. The overall mean percent concentration of ethanol preferred by the hamsters was 24.2 +/- 1.5%. During the following 8-day period when the maximally preferred concentration of ethanol of each hamster was offered with water, the mean intake of ethanol was 17.9 +/- 1.1 g/kg per day. Throughout the test sequence, the caloric intake of the animals was maintained in that calories obtained from food declined at the same rate as the calories obtained from ethanol in rising concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)