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

Changes in serotonin neurotransmission as assayed by microdialysis after acute, intermittent or chronic ethanol administration and withdrawal

BACKGROUND

The serotonergic neurotransmitter system is involved in many ethanol-induced changes, including many behavioural alterations, as well as contributing to alcohol dependence and its withdrawal.

AIMS

This review has evaluated microdialysis studies where alterations in the serotonin system, that is, serotonin, 5-HT, or its metabolite 5-hydroxyindoleacetic acid, 5-HIAA, have been reported during different ethanol intoxication states, as well as in animals showing alcohol preference or not. Changes in 5-HT receptors and the 5-HT transporter are briefly reviewed to comprehend the significance of changes in microdialysate 5-HT concentrations.

MATERIALS AND METHODS

Changes in 5-HT content following acute, chronic and during ethanol withdrawal states are evaluated. In addition, the serotoninergic system was assessed in animals that have been genetically selected for alcohol preference to ascertain whether changes in this monoamine microdialysate content may contribute to alcohol preference.

RESULTS AND DISCUSSION

Changes occurred in 5-HT signalling in the limbic brain regions, increasing after acute ethanol administration in specific brain regions, particularly at higher doses, while chronic alcohol exposure essentially decreased serotonergic transmission. Such changes may play a pivotal role in emotion-driven craving and relapse. Depending on the dosage, mode of administration and consumption rate, ethanol affects specific brain regions in different ways, enhancing or reducing 5-HT microdialysate content, thereby inducing behavioural and cognitive functions and enhancing ethanol consumption.

CONCLUSION

Microdialysis studies demonstrated that ethanol induces several alterations in 5-HT content as well as its metabolites, 5-HIAA and 5-HTOL, not only in its release from a specific brain region but also in the modifications of its different receptor subtypes and its transporter.

Lobeline attenuates ethanol abstinence-induced depression-like behavior in mice

Evidence indicates that the brain nicotinic acetylcholine receptor (nAChRs) ligand lobeline reduces depression-like behaviors, ethanol drinking, and nicotine withdrawal-induced depression-like behaviors. The purpose of the present study was to determine the effects of lobeline on ethanol abstinence-induced depression-like behavior and associated neuroadaptive changes in mice. Adult C57BL/6J male mice were allowed to drink 10% ethanol for 4 weeks using a two-bottle choice procedure. Mice were tested after 24 h and 14 days of ethanol abstinence in a forced swim test (FST), a measure for depression-like behavior. Acute lobeline treatment (1 mg/kg) significantly reduced immobility time compared to controls after 24 h and 14 days of abstinence. In addition, abstinence from chronic ethanol exposure reduced serotonin levels in the hippocampus, which was reversed by acute lobeline treatment. Repeated lobeline treatment (1 mg/kg, once daily) for 14 days during ethanol abstinence also significantly reduced FST immobility in mice exposed to ethanol. Chronic ethanol exposure significantly reduced the number of 5-bromo 2'-deoxyuridine (BrdU)-positive cells in the dentate gyrus of the hippocampus, indicating decreased hippocampal cell proliferation. Abstinence from chronic ethanol exposure also decreased brain-derived neurotrophic factor (BDNF) in the dentate gyrus and CA3 region of the hippocampus. In contrast, repeated lobeline treatment significantly increased both BrdU- and BDNF-positive cells. Taken together, our results indicate that lobeline produced antidepressant-like effects, likely by targeting brain β2-containing nAChRs, serotonergic neurotransmission, and/or hippocampal cell proliferation. Therefore, lobeline may have therapeutic utility to treat alcohol abstinence-induced depression.

Serotonergic Neuroplasticity in Alcohol Addiction

Alcohol addiction is a debilitating disorder producing maladaptive changes in the brain, leading drinkers to become more sensitive to stress and anxiety. These changes are key factors contributing to alcohol craving and maintaining a persistent vulnerability to relapse.

Serotonin (5-Hydroxytryptamine, 5-HT) is a monoamine neurotransmitter widely expressed in the central nervous system where it plays an important role in the regulation of mood. The serotonin system has been extensively implicated in the regulation of stress and anxiety, as well as the reinforcing properties of all of the major classes of drugs of abuse, including alcohol. Dysregulation within the 5-HT system has been postulated to underlie the negative mood states associated with alcohol use disorders.

This review will describe the serotonergic (5-HTergic) neuroplastic changes observed in animal models throughout the alcohol addiction cycle, from prenatal to adulthood exposure. The first section will focus on alcohol-induced 5-HTergic neuroadaptations in offspring prenatally exposed to alcohol and the consequences on the regulation of stress/anxiety. The second section will compare alterations in 5-HT signalling induced by acute or chronic alcohol exposure during adulthood and following alcohol withdrawal, highlighting the impact on the regulation of stress/anxiety signalling pathways. The third section will outline 5-HTergic neuroadaptations observed in various genetically-selected ethanol preferring rat lines. Finally, we will discuss the pharmacological manipulation of the 5-HTergic system on ethanol- and anxiety/stress-related behaviours demonstrated by clinical trials, with an emphasis on current and potential treatments.

iPhone® applications as versatile video tracking tools to analyze behavior in zebrafish (Danio rerio)

Zebrafish (Danio rerio) are emerging as a promising model organism for experimental studies relevant to biological psychiatry. The objective of this study was to develop a novel video-based movement tracking and analysis system to quantify behavioral changes following psychoactive drug exposure in zebrafish. We assessed the effects of withdrawal from chronic ethanol exposure, and subsequent administration of fluoxetine (Prozac®), buspirone (Buspar®), and diazepam (Valium) using two behavioral paradigms; the Novel Tank Diving Test and the Light/Dark Choice Assay. A video tracking system was developed using two Apple® applications (Apps) to quantify these behaviors. Data from zebrafish exposed to the above treatments are presented in this paper not only to exemplify behavioral alterations associated with chronic exposure, but also more importantly, to validate the video tracking system. Following withdrawal from chronic ethanol exposure, zebrafish exhibited dose/time-dependent anxiogenic effects; including reduced exploration and freezing behavior in the Novel Tank Diving Test, and preference for the dark area for the Light/Dark Choice Assay. In contrast, the above drug treatments had significant anxiolytic effects. We have developed a simple and cost-effective method of measuring zebrafish behavioral responses. The iPhone® Apps outlined in this study offer numerous flexible methods of data acquisition; namely, ease of identification and tracking of multiple animals, tools for visualization of the tracks, and calculation of a range of analysis parameters. Furthermore, the limited amount of time required for interpretation of the video data makes this a powerful high-throughput tool with potential applications for pre-clinical drug development.

Biogenic Amines in Striatum of Rats that Had Been Treated with Ethanol, and Their Brains Later Stored in Different Temperatures

The purpose of this study was to investigate how ethanol pretreatment and storage temperatures of brain striatum affect levels of biogenic amines in this tissue. Adult Wistar male rats were injected with 25% ethanol (5.0 g/kg i.p.) while the control rats were administered i.p. with the same volume of saline. Two hours later the rats were decapitated, their brains removed, and the striatum separated. Each striatum was divided into three parts: one part was immediately frozen on dry ice and kept at -70 degrees C; a second fragment was kept in a household refrigerator (+4 degrees C); and the third fragment was kept at +22 degrees C. Twenty-four hours later, levels of DA, DOPAC, HVA, 3-MT, 5-HT, and 5-HIAA in the striatum were assayed by HPLC/ED. Immediately after decapitation; ethanol levels were assayed in the serum of ethanol-pretreated and saline-pretreated rats using gas chromatography. Our results indicate that levels of striatal DA, DOPAC, and HVA in saline-pretreated rats decreased significantly when the storage temperature of the striatum was raised from -70 degrees C, through +4 degrees C, to +22 degrees C, while levels of striatal 5-HT and 5-HIAA remained constant within the temperature range tested and levels of 3-MT fluctuated. In ethanol-pretreated rats, striatal levels of DOPAC, HVA, and 5-HIAA were increased in all three storage temperatures, while levels of DA, 5-HT, and 3-MT were decreased in those temperatures. Those decreases were most profound in striatal samples kept at +22 degrees C. We conclude that concern about possible interactions between drugs and biogenic amines should be exercised.

Effects of risperidone, quetiapine and ziprasidone on ethanol withdrawal syndrome in rats

Comorbid substance use in schizophrenic patients is common, and substance dependence is a predictive factor for psychosis. The present study was designed to investigate the effects of risperidone, quetiapine and ziprasidone, atypical antipsychotic drugs, on ethanol withdrawal syndrome (EWS) in rats. Adult male Wistar rats were used in the study. Ethanol (7.2%, v/v) was given to rats via a liquid diet for 21 days. An isocaloric liquid diet without ethanol was given to control rats. Risperidone (1 and 2 mg/kg), quetiapine (8 and 16 mg/kg), ziprasidone (0.5 and 1 mg/kg) and vehicle were injected into rats intraperitoneally at 1.5 and 5.5 h of ethanol withdrawal. At the 2nd, 4th and 6th hours of ethanol withdrawal, rats were observed for 5 min, and withdrawal signs that included locomotor hyperactivity, stereotyped behaviors, abnormal gait and posture, tail stiffness and agitation were recorded or rated. Following the observations at the 6th hour, the rats were tested for audiogenic seizures. All three drugs had some significant inhibitory effects on EWS-induced behavioral signs beginning at the 2nd hour of withdrawal. The drugs also significantly reduced the incidence of audiogenic seizures. Overall, risperidone and quetiapine seemed to be more effective than ziprasidone in ameliorating the withdrawal signs. Doses of the drugs used in the present study did not produce any significant changes in locomotor activities of naïve rats. Our results suggest that risperidone, quetiapine and ziprasidone had beneficial effects on EWS in rats. Thus, these drugs may be helpful for controlling withdrawal signs in ethanol-dependent patients.

Role of the serotonergic system in alcohol dependence: from animal models to clinics

Alcohol dependence remains among the most common substance abuse problems worldwide, and compulsive alcohol consumption is a significant public health concern. Alcohol is an addictive drug that alters brain function through interactions with multiple neurotransmitter systems. These neurotransmitter systems mediate the reinforcing effects of alcohol. Specifically, the serotonergic system is important in mediating alcohol reward, preference, dependence, and craving. In this review chapter, we first discuss the serotonin system as it relates to alcoholism, and then outline interactions between this system and other neurotransmitter systems. We emphasize the serotonin transporter and its possible role in alcoholism, then present several serotonergic receptors and discuss their contribution to alcoholism, and finally assess the serotonin system as a target for pharmacotherapy, with an emphasis on current and potential treatments.

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

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

Effects of a short-term exposure to alcohol in rats on FAAH enzyme and CB1 receptor in different brain areas

Acute alcohol exposure in rats (8% ethanol in the liquid diet for a period of 24 h) is associated with a decrease in the levels of endocannabinoids (anandamide and 2-arachidonoyl-glycerol) as well as in various N-acylethanolamines, in different brain regions. In the present study, we wanted to further explore: (i) whether these decreases might be caused by an increase in fatty acid amide hydrolase (FAAH), the enzyme involved in the degradation of N-acylethanolamines including anandamide, and (ii) whether the changes in endocannabinoid levels are accompanied by parallel changes in the major cannabinoid receptor type, the CB(1) receptor, activated by these ligands in the brain. Our data proved that FAAH activity did not increase in any of the four regions analyzed, even it was reduced in the hypothalamus and the prefrontal cortex. Paradoxically, FAAH levels increased in the hypothalamus and, to a lesser extent, in the prefrontal cortex and the amygdala, but not in the caudate-putamen. By contrast, the levels of CB(1) receptors were markedly reduced in the amygdala and prefrontal cortex of these rats, although no changes were seen in the hypothalamus and the caudate-putamen. These results suggest that reductions in the levels of endocannabinoids and related N-acylethanolamines caused by acute alcohol exposure are not originated by an enhanced degradation by FAAH enzyme, but they are associated with low levels of the receptors activated by these ligands, although this parallelism did not occur in all brain regions analyzed. In any case, these observations would support the notion of a general reduction in the activity of the cannabinoid signaling system by acute alcohol exposure.

Effects of clozapine on ethanol withdrawal syndrome in rats

AIMS

Co-morbid substance use in schizophrenic patients is common, and an important factor affects the outcome of disease. On the other hand, drug dependence is a predictive factor for psychosis. Alcohol is one of the most frequently abused psychoactive substances and may contribute psychotic symptoms in several conditions, such as withdrawal syndrome. The present study was designed to investigate the effects of clozapine on ethanol withdrawal syndrome (EWS) in rats.

METHODS

Adult male Wistar rats were used in the study. Ethanol (7.2%, v/v) was given to rats by a liquid diet for 14 days. An isocaloric liquid diet without containing ethanol was also given to control rats. Clozapine (2.5, 5 and 10 mg/kg) and its vehicle (0.1% acetic acid) were injected to rats subcutaneously at the 1.5th and 5.5th hours of ethanol withdrawal. At 2nd, 4th and 6th hours of ethanol withdrawal, rats were observed for 5 min and withdrawal signs that included locomotor hyperactivity, agitation, tremor, tail stiffness, stereotyped behaviour and wet dog shakes were recorded or rated. Following the observations at 6th hour, subjects were tested for audiogenic seizures.

RESULTS

Clozapine significantly and dose-dependently inhibited the EWS-induced locomotor hyperactivity, wet dog shake, stereotyped behaviour, tremor and tail stiffness. However, it did not produce any significant effect on agitation and audiogenic seizures. Doses of clozapine used in the present study did not produce any significant change on locomotor activities of naïve rats.

CONCLUSIONS

Our results suggest that clozapine had some significant beneficial effects on EWS in rats. Thus, this drug may be helpful for controlling some withdrawal signs in ethanol-dependent patients.

Enhanced 5-HT(2A) receptor status in the hypothalamus and corpus striatum of ethanol-treated rats

AIM

Brain is the major target for the actions of ethanol and it can affect the brain in a variety of ways. In the present study we have investigated the changes in 5-HT level and the 5-HT(2A) receptors in the ethanol-treated rats.

METHODS

Wistar adult male rats of 180-200 g body weight were given free access to 15% (v/v) (approx.7.5 g/Kg body wt./day) ethanol for 15 days. Controls were given free access to water for 15 days. Brain 5-HT and its metabolites were assayed by high performance liquid chromatography (HPLC) integrated with an electrochemical detector (ECD) fitted with C-18-CLS-ODS reverse phase column. 5-HT(2A) receptor binding assay was done with different concentrations of [3H] MDL 100907.

RESULTS

The hypothalamic 5-HT content significantly increased (P < 0.001) with a decreased (P < 0.001) 5-HIAA/5-HT turnover in the ethanol-treated rats when compared to control. The corpus striatum 5-HT content significantly decreased (P < 0.01) with increased (P < 0.01) 5-HIAA/5- HT turnovers in the ethanol-treated rats when compared to control. Scatchard analysis of [(3)H] MDL 100907 against ketanserin in hypothalamus showed a significant increase (P < 0.001) in B(max )with a decreased affinity (P < 0.001) in ethanol-treated rats when compared to control. The competition curve for [3H] MDL 100907 against ketanserin fitted one-site model in all the groups with unity as Hill slope value. An increased K(i) and log (EC(50)) value were also observed in ethanol-treated rats when compared to control. Scatchard analysis of [3H] MDL 100907 against ketanserin in the corpus striatum of ethanol-treated rats showed a significant increase (P < 0.001) in B(max) and in affinity (P < 0.01) when compared to control. The change in affinity of the receptor protein in both corpus striatum and hypothalamus shows an altered receptor. The competition curve for [(3)H] MDL 100907 against ketanserin fitted one-site model in all the groups with unity as Hill slope value. There was no significant change in K(i) and log (EC (50)) value in ethanol-treated rats when compared to control.

CONCLUSION

The present study demonstrated the enhanced 5-HT(2A) receptor status in hypothalamus and corpus striatum. The ethanol-induced enhanced 5-HT(2A) receptors in the hypothalamus and corpus striatum has clinical significance in the better management of ethanol addiction. This will have therapeutic application.

Effects of olanzapine on ethanol withdrawal syndrome in rats

The present study was designed to investigate the effects of olanzapine, a serotonin-dopamine antagonistic atypical antipsychotic agent, on ethanol withdrawal syndrome in rats. Adult male Wistar rats were subjects. Ethanol (7.2%, v/v) was given to rats by a liquid diet for 21 days. Control rats were pair fed with an isocaloric liquid diet containing sucrose as a caloric substitute to ethanol. After 2nd, 4th and 6th h of ethanol withdrawal, rats were observed for 5 min, afterwards withdrawal signs that included locomotor hyperactivity, agitation, stereotyped behavior, tremor, wet dog shakes, abnormal posture and abnormal gait were recorded or rated. Olanzapine (0.5, 1 and 2 mg/kg) and saline were injected to the rats intraperitoneally 30 min before ethanol withdrawal assessment. A second series of injections was also given 30 min before the 6th-h-observation, and subjects were then tested for audiogenic seizures. Olanzapine (2 mg/kg) produced significant inhibitory effects on stereotyped behaviors and wet dog shakes at the 6th h of ethanol withdrawal. Contrary, the same dose caused some increases in the intensity of posture and gait impairments at the 2nd h of ethanol withdrawal. In addition, that dose was found to be ineffective on agitation, tremor, tail stiffness and audiogenic seizures. Our results suggest that acute olanzapine treatment has beneficial effects on stereotyped behavior and wet dog shakes, but it also has some adverse effects on posture and gait during ethanol withdrawal in rats. Overall, olanzapine does not seem to be an adequate and suitable drug in controlling of ethanol withdrawal syndrome.

Short-term exposure to alcohol in rats affects brain levels of anandamide, other N-acylethanolamines and 2-arachidonoyl-glycerol

Chronic alcohol exposure leads to significant changes in the levels of endocannabinoids and their receptors in the brains of humans and laboratory animals, as well as in cultured neuronal cells. However, little is known about the effects of short-term periods of alcohol exposure. In the present study, we examined the changes in endocannabinoid levels (anandamide and 2-arachidonoylglycerol), as well as four additional N-acylethanolamines, in four brain regions of rats exposed to alcohol through the liquid diet for a period of 24h. The levels of N-acylethanolamines were diminished 24h after the onset of alcohol exposure. This was particularly evident for anandamide in the hypothalamus, amygdala and caudate-putamen, for N-palmitoylethanolamine in the caudate-putamen, for N-oleoylethanolamine in the hypothalamus, caudate-putamen and prefrontal cortex, and for N-stearoylethanolamine in the amygdala. The only exception was N-linoleoylethanolamine for which the levels increased in the amygdala after the exposure to alcohol. The levels of the other major endocannabinoid, 2-arachidonoylglycerol, were also reduced with marked effects in the prefrontal cortex. These results support the notion that short-term alcohol exposure reduces endocannabinoid levels in the brain accompanied by a reduction in several related N-acylethanolamines.

Effects of escitalopram on ethanol withdrawal syndrome in rats

The present study was designed to investigate the effects of escitalopram, a selective serotonin reuptake inhibitor, on ethanol withdrawal syndrome in rats. Adult male Wistar rats (266-278 g) were subjects. Ethanol (7.2%, v/v) was given to rats by a liquid diet for 21 days. Control rats were pair fed with an isocaloric liquid diet containing sucrose as a caloric substitute to ethanol. Escitalopram (2.5, 5 and 10 mg/kg) and saline were injected to rats intraperitoneally just before ethanol withdrawal. After the second and sixth hours of ethanol withdrawal, rats were observed for 5 min, and withdrawal signs that included locomotor hyperactivity, agitation, stereotyped behavior, wet dog shakes, tremors and audiogenic seizures were recorded or rated. A second series of injections was given 30 min before sixth hour of withdrawal test. Effects of escitalopram on the locomotor activities of the naïve (no ethanol-dependent) rats were also evaluated. Escitalopram (5 mg/kg) reduced the increased stereotyped behaviors at the sixth hour of ethanol withdrawal. It inhibited tremors at the second hour of ethanol withdrawal at doses of 5 and 10 mg/kg. Escitalopram (2.5 and 5 mg/kg) also produced some significant attenuations in the incidence of wet dog shakes at the second and sixth hours of the observation period. It was found ineffective on locomotor hyperactivity, agitation and audiogenic seizures. Escitalopram (2.5 and 5 mg/kg) did not cause any significant effect on locomotor activities of the naïve rats. Our results suggest that acute escitalopram treatment has some limited beneficial effects on ethanol withdrawal syndrome in rats.

Acute and chronic tianeptine treatments attenuate ethanol withdrawal syndrome in rats

Effects of acute and chronic tianeptine treatments on ethanol withdrawal syndrome were investigated in rats. Ethanol (7.2% v/v) was given to adult male Wistar rats by a liquid diet for 30 days. Acute or chronic (twice daily) tianeptine (5, 10 and 20 mg/kg) and saline were administered to rats intraperitoneally. Acute and last chronic tianeptine injections and saline were done 30 min before ethanol withdrawal testing. After 2nd, 4th and 6th hours of ethanol withdrawal, rats were observed for 5 min, and withdrawal signs which included locomotor hyperactivity, agitation, tremor, wet dog shakes, stereotyped behavior and audiogenic seizures were recorded or rated. Locomotor activity in naive (no ethanol-dependent rats) was also tested after acute tianeptine treatments. Acute but not chronic tianeptine treatment attenuated locomotor hyperactivity and agitation in ethanol-dependent rats. Both acute and chronic tianeptine treatment produced some significant inhibitory effects on tremor, wet dog shakes, stereotyped behaviors and audiogenic seizures during the ethanol withdrawal. Our results suggest that acute or chronic tianeptine treatment attenuates ethanol withdrawal syndrome in ethanol-dependent rats and this drug may be useful for treatment of ethanol-type dependence.

Effects of venlafaxine on ethanol withdrawal syndrome in rats

The present study was designed to investigate the effects of venlafaxine, a serotonin and noradrenaline reuptake inhibitor (SNRI), on ethanol withdrawal syndrome in rats. Adult male Wistar rats (187-319 g) were used for the study. Ethanol (7.2%, v/v) was given to rats by a liquid diet for 21 days. Control rats were pair-fed an isocaloric liquid diet containing sucrose as a caloric substitute to ethanol. Venlafaxine (5, 10, 20 and 40 mg/kg) and saline were injected to rats intraperitoneally just before ethanol withdrawal. After the 2nd, 4th and 6th hour of ethanol withdrawal, rats were observed for 5 min, and withdrawal signs that included locomotor hyperactivity, agitation, stereotyped behaviour and wet dog shakes were recorded or rated. A second series of injections was given at the 6th hour after the first one, and rats were then tested for audiogenic seizures. Venlafaxine produced some inhibitory effects on locomotor hyperactivity, stereotypic behaviours and wet dog shakes. However, a two-way anova of the data did not indicate any significant effect. It reduced the incidence of the audiogenic seizures at the 6th hour of ethanol withdrawal. Venlafaxine (20 mg/kg) also prolonged the latency of the seizures significantly. Our results suggest that acute venlafaxine treatment has limited beneficial effects on ethanol withdrawal syndrome in rats.

Effects of fluoxetine on ethanol withdrawal syndrome in rats

The present study was designed to investigate the effects of fluoxetine, a selective serotonin reuptake inhibitor, on ethanol withdrawal syndrome in rats. Adult male Wistar rats (218-255 g) were subjects. Ethanol (7.2%, v/v) was given to rats by a liquid diet for 21 days. Control rats were pair fed an isocaloric liquid diet containing sucrose as a caloric substitute to ethanol. Fluoxetine (2.5, 5 and 10 mg/kg) and saline were injected to rats intraperitoneally just before ethanol withdrawal. After 2nd, 4th and 6th hour of ethanol withdrawal, rats were observed for 5 min, and withdrawal signs that included locomotor hyperactivity, agitation, stereotyped behavior, wet dog shakes and tremor were recorded or rated. A second series of injections was given at 6 h after the first one, and subjects were then tested for audiogenic seizures. Fluoxetine produced some dose-dependent and significant inhibitory effects on all the signs of ethanol withdrawal during ethanol withdrawal period. Our results suggest that acute fluoxetine treatment has some beneficial effects on ethanol withdrawal in rats. Thus, this drug may be useful for treatment of ethanol withdrawal syndrome.

Changes in endocannabinoid contents in the brain of rats chronically exposed to nicotine, ethanol or cocaine

Despite recent data suggesting that the endocannabinoid transmission is a component of the brain reward system and plays a role in dependence/withdrawal to different habit-forming drugs, only a few studies have examined changes in endocannabinoid ligands and/or receptors in brain regions related to reinforcement processes after a chronic exposure to these drugs. Recently, we carried out a comparative analysis of the changes in cannabinoid CB(1) receptor density in several rat brain regions caused by chronic exposure to some of the most powerful habit-forming drugs. In the present study, we have extended this objective by examining changes in the brain contents of arachidonoylethanolamide (AEA) and 2-arachidonoyl-glycerol (2-AG), the endogenous ligands for cannabinoid receptors, in animals chronically exposed to cocaine, nicotine or ethanol. Results were as follows. Cocaine was the drug exhibiting the minor number of effects, with only a small, but significant, decrease in the content of 2-AG in the limbic forebrain. In contrast, chronic alcohol exposure caused a decrease in the contents of both AEA and 2-AG in the midbrain, while it increased AEA content in the limbic forebrain. This latter effect was also observed after chronic nicotine exposure together with an increase in AEA and 2-AG contents in the brainstem. In contrast, the hippocampus, the striatum and the cerebral cortex exhibited a decrease in AEA and/or 2-AG contents after chronic nicotine exposure. We also tested the effect of chronic nicotine on brain CB(1) receptors, which had not been investigated before, and found an almost complete lack of changes in mRNA levels or binding capacity for these receptors. In summary, our results, in concordance with previous data on CB(1) receptors, indicate that the three drugs tested here produce different changes in endocannabinoid transmission. Only in the case of alcohol and nicotine, we observed a common increase in AEA contents in the limbic forebrain. This observation is important considering that this region is a key area for the reinforcing properties of habit-forming drugs, which might support the involvement of endocannabinoid transmission in some specific events of the reward system activated by these drugs.

Regional and cellular expression of CYP2D6 in human brain: higher levels in alcoholics

Cytochrome P450 (CYP) 2D6 is expressed in liver, brain and other extrahepatic tissues where it metabolizes a range of centrally acting drugs and toxins. As ethanol can induce CYP2D in rat brain, we hypothesized that CYP2D6 expression is higher in brains of human alcoholics. We examined regional and cellular expression of CYP2D6 mRNA and protein by RT-PCR, Southern blotting, slot blotting, immunoblotting and immunocytochemistry. A significant correlation was found between mean mRNA and CYP2D6 protein levels across 13 brain regions. Higher expression was detected in 13 brain regions of alcoholics (n = 8) compared to nonalcoholics (n = 5) (anovap < 0.0001). In hippocampus this was localized in CA1-3 pyramidal cells and dentate gyrus granular neurons. In cerebellum this was localized in Purkinje cells and their dendrites. Both of these brain regions, and these same cell-types, are known to be susceptible to alcohol damage. For one case, a poor metabolizer (CYP2D6*4/*4), there was no detectable CYP2D6 protein, confirming the specificity of the antibody used. These data suggest that in alcoholics elevated brain CYP2D6 expression may contribute to altered sensitivity to centrally acting drugs and to the mediation of neurotoxic and behavioral effects of alcohol.

Chronic exposure to morphine, cocaine or ethanol in rats produced different effects in brain cannabinoid CB(1) receptor binding and mRNA levels

Recent evidence suggest that the endocannabinoid system might be a component of the brain reward system and, then, play a role, not only in cannabinoid tolerance/dependence, but also in dependence/withdrawal to other drugs of abuse. However, there are not many studies that compare the changes in endocannabinoid ligands and/or receptors in brain regions (particularly in those areas related to reinforcement processes) during dependence to opiates, cocaine or alcohol. The present study addressed this objective, by examining the changes in CB(1) receptor binding (measured by [3H]-CP55,940 autoradiography) and its mRNA levels (measured by in situ hybridization) in different brain regions of animals chronically exposed to morphine, cocaine or ethanol. The results showed that these three drugs produced different changes in CB(1) receptor binding and mRNA levels, a finding that precludes the existence of a common alteration of the endocannabinoid system during dependence states to these habit-forming drugs. Thus, chronic ethanol exposure was usually uneffective in altering both CB(1) receptor binding and mRNA levels in all regions examined. In contrast, chronic cocaine exposure produced significant changes only at the level of CB(1) receptor mRNA, with decreases of the transcript levels in the ventromedial hypothalamic nucleus and the superficial and deep layers of the cerebral cortex, but no changes in the hippocampal, motor and limbic structures. Finally, chronic morphine exposure increased the density of CB(1) receptors in the medial caudate-putamen, but decreased their mRNA levels in this region and also in the lateral caudate-putamen and the cerebellum. In limbic structures, chronic morphine exposure increased both binding and mRNA levels for CB(1) receptors in the septum nuclei. Binding was also increased in the nucleus accumbens, but reduced in the basolateral amygdala. In hippocampal structures, chronic morphine exposure reduced CB(1) receptor binding in the dentate gyrus, although mRNA levels were unaffected in this region, but increased in the CA2 subfield of the Ammon's horn. The results indicate that mechanisms of dependence for alcohol, cocaine and morphine are different in terms of their impact on the endocannabinoid system. Alcohol did not produce any effects on CB(1) receptor binding and mRNA levels, whereas cocaine only affected transcript levels in selected regions and morphine produced divergent and region-dependent effects.