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The present study examined the involvement of GABA(A) and GABA(B) receptors in the discriminative stimulus effects of gamma-hydroxybutyric acid (GHB). Rats were trained to discriminate either 300 or 700 mg/kg GHB IG from water using a T-maze, food-reinforced drug-discrimination procedure. The direct GABA(B) agonist, baclofen, substituted completely for both training doses of GHB; its potency to substitute for GHB increased moderately as the training dose of GHB was increased. The positive GABA(A) modulator, diazepam, substituted partially for 300 mg/kg GHB, but failed to elicit GHB-appropriate responding in rats trained with the higher GHB dose. Finally, the GABA(B) antagonist, CGP 35348, completely blocked the discriminative stimulus effects of the high training dose of GHB, but only partially antagonized the effects of the low training dose. These results suggest that (a) GHB produces a compound stimulus, and (b) both GABA(B)- and GABA(A)-mediated cues are prominent components of this compound stimulus; the contribution of each component, however, appears to vary as the training dose of GHB is increased.

The present study demonstrates that the gamma-hydroxybutyric acid receptor antagonist, NCS-382, markedly reduces blood ethanol levels (BELs) in rats when ethanol is administered via the intragastric route, whereas it is completely ineffective when ethanol is injected IP. The reducing effect of NCS-382 on BELs is likely due to a lessened absorption of ethanol from the gastrointestinal tract.

Sleep deprivation (SD) is known to induce perceptual impairments, ranging from perceptual distortion to hallucinatory states. Although this phenomenon has been extensively described in the literature, its neurobiological underpinnings remain elusive. In rodents, SD induces a series of behavioural patterns that might be reflective of psychosis and mania, such as hyperlocomotion and sensitization to psychotogenic drugs. Notably, such changes are accompanied by transitory alterations of dopaminergic signalling. Based on the hypothesis that both psychotic and manic disorders reflect gating impairments, the present study was aimed at the assessment of the impact of SD on the behavioural model of prepulse inhibition (PPI) of the startle reflex, a reliable paradigm for the study of informational filtering. Rats subjected to SD (24 h, 48 h, 72 h) exhibited a time-dependent increase in startle reflex and a dramatic deficit in PPI. Both alterations were reversed 24 h after termination of the SD period. Interestingly, PPI disruption was efficiently prevented by haloperidol (0.1 mg/kg i.p.) clozapine (5 mg/kg i.p.) and risperidone (1 mg/kg i.p.). Conversely, neither the anxiolytic diazepam (5 mg/kg i.p.) nor the antidepressant citalopram (5 mg/kg i.p) affected the PPI disruption mediated by SD, although diazepam reversed the enhancement in startle reflex magnitude induced by this manipulation. Our data suggest that SD induces gating deficits that might be relevant to the hallucinatory phenomena observed in humans, and provide a novel reliable animal model where such relationship can be studied.

Pharmacological blockade of the cannabinoid CB1 receptor has been repeatedly reported to suppress intake of food, including highly palatable foods, in laboratory animals. This study was designed to investigate whether treatment with the cannabinoid CB1 receptor antagonist, rimonabant, would reduce the reinforcing and motivational properties of a chocolate-flavoured beverage [containing 5% (w/v) chocolate powder] in nonfood-deprived and nonwater-deprived Wistar rats trained to self-administer this beverage under an operant conditioning procedure. This study was also aimed at assessing to what degree self-administration behaviour could be manipulated environmentally. After a period of training and maintenance of the self-administration behaviour, separate groups of rats were exposed to different experimental conditions [session length varying from 20 to 120 min; fixed ratio (FR) schedule of reinforcement varying from FR10 to FR40; reinforcer presentation varying from 2.5 to 10 s; concentration of the chocolate powder varying from 5% (w/v) to 0%]; other rat groups were used to test the effect of acute and repeated treatment with rimonabant (1-5.6 mg/kg, intraperitoneally) on two schedules of reinforcement (FR10 and progressive ratio) and extinction responding. All rats rapidly acquired and steadily maintained high levels of self-administration of the chocolate-flavoured beverage. Changes in experimental conditions modified the rats' self-administration behaviour; these changes seemed to be the result of the rats' attempt to adjust their behaviour so as to consume as much of the chocolate-flavoured beverage as possible when it was presented at its most palatable 5% concentration. Treatment with rimonabant dose-dependently suppressed self-administration of the chocolate-flavoured beverage. When rimonabant was administered repeatedly, only a modest degree of tolerance developed to its reducing effect. Finally, treatment with rimonabant resulted in a dose-dependent reduction of the motivational properties of the chocolate-flavoured beverage, measured by the progressive ratio schedule of reinforcement and extinction-responding procedure. These results suggest that self-administration of a chocolate-flavoured beverage can be rapidly and reliably established in rats and that this behaviour is environmentally manipulable. These results also suggest that the cannabinoid CB1 receptor is a crucial component of the neural substrate mediating the reinforcing and motivational properties of a highly palatable food such as a chocolate-flavoured beverage.

Recent evidence indicates that neuroactive steroids may participate in the pathogenesis of schizophrenia spectrum disorders, yet the mechanisms of this involvement are elusive. As 5-alpha-reductase (5AR) is the rate-limiting enzyme of one of the two major metabolic pathways in brain steroidogenesis, we investigated the effects of its blockade in several rat models of psychotic-like behavior. The 5AR inhibitor finasteride (FIN, 60 or 100 mg/kg, intraperitoneal, i.p.) dose- and time-dependently antagonized prepulse inhibition (PPI) deficits induced by apomorphine (APO, 0.25 mg/kg, subcutaneous, s.c.) and d-amphetamine (AMPH, 5 mg/kg, s.c.), in a manner analogous to haloperidol (HAL, 0.1 mg/kg, i.p.) and clozapine (CLO, 5 mg/kg, i.p.). Similar results were observed with the other 5AR inhibitors dutasteride (DUT, 40 or 80 mg/kg, i.p.) and SKF 105111 (30 mg/kg, i.p.). FIN (60 or 100 mg/kg, i.p.) also reduced hyperlocomotion induced by AMPH (1 or 3 mg/kg, s.c.) and attenuated stereotyped behaviors induced by APO (0.25 mg/kg, s.c.). Nevertheless, FIN (100 mg/kg, i.p.) did not reverse the PPI disruption induced by the N-methyl-d-aspartate receptor antagonist dizocilpine (0.1 mg/kg, s.c.). FIN (60-300 mg/kg, i.p.) induced no catalepsy in either the bar test or the paw test. Our results suggest that 5AR inhibitors elicit antipsychotic-like effects in animals and may be proposed as a putative novel target in the management of psychotic disorders.

Dopamine and noradrenaline are both involved in modulation of superior cognitive functions that are mainly dependent on frontal cortex activity. Experimental evidence points to parallel variations in extracellular concentrations of catecholamines in the cerebral cortex, which leads us to hypothesize their corelease from noradrenergic neurons. This study aimed to verify this hypothesis, by means of cerebral microdialysis following destruction of dopaminergic innervation in rats. The unilateral injury of dopaminergic neurons, by 6-hydroxydopamine injection in the ventral tegmental area, dramatically reduced the immunoreactivity for dopamine transporter in the cerebral hemisphere ipsilateral to the lesion. Tissue dopamine content in the ipsilateral nucleus accumbens and medial prefrontal and parietal cortex was also profoundly decreased, whereas noradrenaline was only slightly affected. Despite the lower tissue content in the denervated side, the extracellular dopamine level was not changed in the cortex, although it was markedly decreased in the nucleus accumbens ipsilateral to the lesion. The effect of drugs selective for D(2)-dopaminergic (haloperidol) or alpha(2)-noradrenergic (RS 79948) receptors was verified. Haloperidol failed to modify extracellular dopamine in either cortex but increased it in the nucleus accumbens, such an increase being greatly reduced in the denervated side. On the other hand, RS 79948 increased extracellular dopamine and DOPAC in all areas tested, the increases being of the same degree in both intact and lesioned sides. The results strongly support the hypothesis that the majority of extracellular dopamine in the cortex, unlike that in the nucleus accumbens, originates from noradrenergic terminals.

The intracerebroventricular injection (1 microgram) of murine corticotropin-releasing factor (r-CRF) to rats after 72 h of sleep deprivation markedly postponed the sleep onset, reduced slow wave sleep and prolonged the duration of paradoxical sleep (PS) episodes. Moreover, CRF is-to our knowledge-the first compound to be able to further prolong PS in a condition (sleep deprivation) in which its duration is already increased. Our findings raise the possibility that CRF might play a physiological role in the regulation of the sleep-wakefulness cycle.

Aims: Rats avidly consume non-alcoholic beer, and addition of alcohol to non-alcoholic beer may function as a medium to induce intake of large amounts of alcohol in rats. The present study investigated whether Sardinian alcohol-preferring (sP) and Sardinian non-preferring (sNP) rats, initially exposed to non-alcoholic beer, and subsequently to non-alcoholic beer containing increasing concentrations of alcohol, would develop unusually high alcohol self-administration and drinking behaviours: (i) when alcohol was added to non-alcoholic beer, and (2) once beer was withdrawn and a plain alcohol solution was made available. Methods: In Experiment 1, rats were exposed to operant, 30-min/day self-administration sessions of non-alcoholic beer with increasing concentrations of alcohol (0, 2.5, 5, 7.5, and 10% (v/v)) for a total of 45 days. After a brief 'beer-fading' phase, the rats were exposed to self-administration sessions of a plain 10% (v/v) alcohol solution. In Experiment 2, the rats were exposed to non- alcoholic beer with increasing concentrations of alcohol (0, 2.5, 5, 7.5, and 10% (v/v)) and water under the 2-bottle choice regimen with unlimited access (24 h/day) for a total of 35 days. After a brief 'beer-fading' phase, the rats were exposed to the choice between a plain 10% (v/v) alcohol solution and water. Results: sP and sNP rats did not differ in self-administration (Experiment 1) and intake (Experiment 2) of non-alcoholic beer. In Experiment 1, as alcohol content increased, the amount of self-administered alcohol increased progressively in sP rats (up to 1-1.2 g/kg) and remained stable in sNP rats (approximately 0.65 g/kg). When the plain 10% alcohol solution was available, the amount of self-administered alcohol in sP rats initially dropped, and tended to increase—up to approximately 0.6 g/kg—on continuing exposure. In sNP rats, their lever-pressing behaviour was rapidly extinguished after beer withdrawal. In Experiment 2, as alcohol content was increased, daily alcohol intake increased progressively in sP rats (up to 8-9 g/kg) and averaged approximately 2.4 g/kg in sNP rats. When the plain alcohol solution was available, daily alcohol intake in sP rats was initially low, reaching control values on continuing exposure; conversely, daily alcohol intake was completely suppressed in sNP rats. Conclusions: These results suggest that exposure to alcoholic beer resulted in unusually high intakes of alcohol in both sP and sNP rats for as long as non-alcoholic beer was added to alcohol; however, these high levels of alcohol self-administration and intake were not maintained once non-alcoholic beer was withdrawn.

γ-Hydroxybutyric acid (GHB) reduces alcohol drinking, promotes abstinence from alcohol, suppresses craving for alcohol, and ameliorates alcohol withdrawal syndrome in alcoholics. At preclinical level, GHB suppresses alcohol withdrawal signs and alcohol intake in rats. The present study was designed to investigate whether GHB administration was capable of affecting alcohol's motivational properties (the possible animal correlate of human craving for alcohol) in selectively bred Sardinian alcohol-preferring rats. To this aim, rats were initially trained to lever press for alcohol (15%, vol/vol) under a procedure of operant, oral alcohol self-administration (fixed ratio 4 in 30-min daily sessions). Once responding for alcohol had stabilized, rats were divided into two groups and allocated to two independent experiments. Experiment 1 assessed the effect of GHB (0, 25, 50, and 100 mg/kg, i.p.) on breakpoint for alcohol, defined as the lowest response requirement not achieved by each rat when exposed to a single-session progressive ratio schedule of reinforcement. Experiment 2 assessed the effect of GHB (0, 25, 50, and 100 mg/kg, i.p.) on single-session extinction responding for alcohol (alcohol was absent and unreinforced responding was recorded). Breakpoint and extinction responding for alcohol are reliable indexes of alcohol's motivational strength. In Experiment 1, all doses of GHB reduced—by approximately 20% in comparison to saline-treated rats—breakpoint for alcohol. In Experiment 2, administration of 25, 50, and 100 mg/kg GHB reduced—by approximately 25%, 40%, and 50%, respectively, in comparison to saline-treated rats—extinction responding for alcohol. Conversely, no dose of GHB altered breakpoint and extinction responding for sucrose (3%, wt/vol) in two independent subsets of Sardinian alcohol-preferring rats. Together, these data suggest that GHB administration specifically suppressed alcohol's motivational properties in Sardinian alcohol-preferring rats. These results are consistent with the anticraving properties of GHB observed in clinical studies.

In 42 alcoholic inpatients we performed an open randomized study to compare the effects of diazepam and gamma-hydroxybutyrate (GHB) on the suppression of severe alcohol withdrawal syndrome and hypercortisolism. Both diazepam (.5 mg/kg bodyweight, q.i.d.) and GHB (50 mg/kg bodyweight, q.i.d.) were orally administered for three weeks. During all study period, GHB was more able than diazepam in reducing both withdrawal syndrome and hypercortisolism. These effects were evident during the first week of treatment and persisted throughout the study period. The results confirm a strict correlation between high levels of plasma cortisol and alcohol withdrawal symptoms and they show a slight superiority of GHB over diazepam in the suppression of both ethanol withdrawal and hypercortisolism. Taken together, our data suggest that GHB may act as potent anti-withdrawal agent in severe abstinent alcoholics.

Gamma-amino-butyric acid (GABA)(B) receptors play a key role in the pathophysiology of psychotic disorders. We previously reported that baclofen, the prototypical GABA(B) agonist, elicits antipsychotic-like effects in the rat paradigm of prepulse inhibition (PPI) of the startle, a highly validated animal model of schizophrenia.We studied the role of GABA(B) receptors in the spontaneous PPI deficits displayed by DBA/2J mice.We tested the effects of baclofen (1.25-5 mg/kg, intraperitoneal [i.p.]) in DBA/2J and C57BL/6J mice, in comparison to the antipsychotic drugs haloperidol (1 mg/kg, i.p.) and clozapine (5 mg/kg, i.p.). Furthermore, we investigated the expression of GABA(B) receptors in the brain of DBA/2J and C57BL/6J mice by quantitative autoradiography.Baclofen dose-dependently restored PPI deficit in DBA/2J mice, in a fashion similar to the antipsychotic clozapine (5 mg/kg, i.p.). This effect was reversed by pretreatment with the GABA(B) antagonist SCH50211 (50 mg/kg, i.p.). In contrast, baclofen did not affect PPI in C57BL/6J mice. Finally, quantitative autoradiographic analyses assessed a lower GABA(B) receptor expression in DBA/2J mice in comparison to C57BL/6J controls in the prefrontal cortex and hippocampus but not in other brain regions.Our data highlight GABA(B) receptors as an important substrate for sensorimotor gating control in DBA/2J mice and encourage further investigations on the role of GABA(B) receptors in sensorimotor gating, as well as in the pathophysiology of psychotic disturbances.

Cannabis is widely abused by women at reproductive age and during pregnancy. Animal studies showed a particular vulnerability of the developing brain to prenatal chronic cannabinoid administration. We determined whether prenatal exposure to WIN 55,212-2, a potent cannabinoid receptor agonist, affected (1) density, affinity and/or function of cannabinoid CB(1) receptors, (2) endogenous levels of the endocannabinoid anandamide, (3) activities of the major anandamide synthesising and hydrolysing enzymes, N-acyl-phosphatidylethanolamine-specific phospholipase D (NAPE-PLD) and fatty acid amide hydrolase (FAAH), respectively, in brain areas of adult male offspring rats. Furthermore, the effect of prenatal WIN 55,212-2 on spontaneous motility was analyzed. Pregnant rats were treated daily with WIN 55,212-2 (0.5 mg/kg, gestation day 5-20) or vehicle. [(3)H]CP 55,940 and WIN 55,212-2-stimulated [(35)S] GTPgammaS binding were carried out in cerebellum, cerebral cortex, hippocampus, striatum and limbic areas of male adult offspring. Levels of anandamide, FAAH and NAPE-PLD activity were also determined. EC(50) values for WIN 55,212-2-stimulated [(35)S]GTPgammaS binding were significantly different in hippocampus (-26%) and striatum (+27%) in WIN 55,212-2-treated rats. Cannabinoid CB(1) receptor density and affinity were not affected in any analyzed region. In the striatum, increased anandamide levels were associated with reduced FAAH and enhanced NAPE-PLD activities. Opposite changes in anandamide levels and enzymatic activities were detected in limbic areas of WIN 55,212-2-treated rats. Ambulatory activity between WIN 55,212-2- and vehicle-treated adult offspring did not vary. Our results show that prenatal exposure to cannabinoid agonist induces a long-term alteration of endocannabinoid system in brain areas involved in learning-memory, motor activity and emotional behavior.

The endocannabinoids anandamide and 2-arachidonoyglycerol (2-AG) may contribute to the regulation of mood and emotion. In this study, we investigated the impact of the endocannabinoid transport inhibitor AM404 on three rat models of anxiety: elevated plus maze, defensive withdrawal and separation-induced ultrasonic vocalizations. AM404 (1-5 mg kg-1, intraperitoneal (i.p.)) exerted dose-dependent anxiolytic-like effects in the three models. These behavioral effects were associated with increased levels of anandamide, but not 2-AG, in the prefrontal cortex and were prevented by the CB1cannabinoid antagonist rimonabant (SR141716A), suggesting that they were dependent on anandamide-mediated activation of CB1cannabinoid receptors. We also evaluated whether AM404 might influence motivation (in the conditioned place preference (CPP) test), sensory reactivity (acoustic startle reflex) and sensorimotor gating (prepulse inhibition (PPI) of the startle reflex). In the CPP test, AM404 (1.25-10 mg kg-1, i.p.) elicited rewarding effects in rats housed under enriched conditions, but not in rats kept in standard cages. Moreover, AM404 did not alter reactivity to sensory stimuli or cause overt perceptual distortion, as suggested by its lack of effect on startle or PPI of startle. These results support a role of anandamide in the regulation of emotion and point to the anandamide transport system as a potential target for anxiolytic drugs. © 2006 Nature Publishing Group All rights reserved.

A severe and life-threatening gamma-hydroxybutyric acid (GHB) withdrawal syndrome, clinically similar to the alcohol withdrawal syndrome, is increasingly being reported in GHB addicts. We investigated for the occurrence of withdrawal in Wistar and Sprague-Dawley rats, and in the selectively bred lines of GHB-sensitive (GHB-S) and Sardinian alcohol-preferring (sP) rats, following chronic administration of GHB, gamma-butyrolactone (GBL), and/or 1,4-butanediol (1,4-BD). Using validated rodent alcohol withdrawal scoring scales, little to no spontaneous or pharmacologically precipitated withdrawal effects were observed in Wistar, Sprague-Dawley, or GHB-S rats. Conversely, sP rats displayed both spontaneous and precipitated audiogenic seizures following abrupt cessation of chronic GHB or 1,4-BD administration and following pharmacological challenge with the GABA(B) receptor-selective antagonist, SCH 50911, respectively.

Several lines of preclinical evidence indicate the ability of the prototypic cannabinoid CB(1) receptor antagonist, rimonabant, to suppress various alcohol-related behaviors, including alcohol drinking and seeking behavior and alcohol self-administration in rats and mice. Together, these data-synthetically reviewed in the present paper-suggest (a) the involvement of the cannabinoid CB(1) receptor in the neural substrate controlling alcohol intake, alcohol reinforcement, and the motivational properties of alcohol and (b) that rimonabant may constitute a new and potentially effective medication for the treatment of alcohol dependence.

Endocannabinoid-mediated forms of transient synaptic depression have been described in several brain structures, including the dopaminergic ventral tegmental area (VTA). However, their functional and/or behavioural correlates are yet to be determined. The present study was designed to investigate whether back-propagating action potentials in dopamine (DA) neurons, evoked by the stimulation of the medial forebrain bundle (MFB), could trigger endocannabinoid-mediated forms of synaptic modulation. The MFB contains axons ascending from DA neurons to the nucleus accumbens and other forebrain structures, and its stimulation is rewarding because it elicits intra-cranial self-stimulation. Single cell extracellular recordings were carried out from anti-dromically identified VTA DA neurons in chloral hydrate anesthetized rats. DA neurons responded to MFB stimulation (1 s, 20–80 Hz) with a frequency-dependent increase in spontaneous firing rate, which was enhanced by the cannabinoid type-1 receptor antagonist SR141716A (1 mg/kg) and depressed by the agonist WIN55212-2 (0.125 mg/kg). Increasing brain levels of the endocannabinoid anandamide by blocking its major hydrolysing enzyme, fatty-acid amide hydrolase, with URB597 (0.1 mg/kg) was ineffective, whereas blockade of the endocannabinoid membrane transporter with UCM707 (1 mg/kg) enhanced post-stimulus firing rate. Our study indicates that stimulation of the MFB evokes an endocannabinoid-mediated short-term modulation of DA neuron activity. Thus, endocannabinoids might play an important role in the mechanisms underlying the rewarding properties of MFB stimulation.

1. This study investigated whether (a) cannabinoid CB(1) receptor knockout (CB(1)(-/-)) mice displayed altered gastrointestinal transit and (b) cannabinoid CB(1) and opioid receptors functionally interact in the regulation of gastrointestinal transit. 2. Gastrointestinal transit was assessed by the Whole Gastrointestinal Transit, measuring the excretion time of an intragastrically administered marker (whole intestine), and the Upper Gastrointestinal Transit, measuring the distance covered by the marker in the small intestine. 3. CB(1)(-/-) and homozygous CB(1)(+/+) (CB(1)(+/+)) mice did not differ in both whole gut and small intestine transit. CB(1)(-/-) and CB(1)(+/+) mice were equally responsive to the inhibitory effect of morphine (10 mg kg(-1)) and loperamide (3 mg kg(-1)) on whole gut transit.4. Additionally, in CD1 mice the cannabinoid CB(1) receptor antagonist, rimonabant (0-0.5 mg kg(-1)), failed to block the inhibitory effect of morphine (0-1.25 mg kg(-1)) and loperamide (0-0.5 mg kg(-1)) on transit in small and whole intestine. Similarly, the opioid receptor antagonists, naloxone (0-1 mg kg(-1)) and naltrexone (0-10 mg kg(-1)), failed to block the inhibitory effect of the cannabinoid WIN 55,212-2 (0-3 mg kg(-1)) on transit in small and whole intestine.5. These results suggest that (a) compensatory mechanisms likely developed in CB(1)(-/-) mice to overcome the lack of inhibitory function of endocannabinoid system; (b) cannabinoid and opioid receptor systems did not interact in regulating gastrointestinal transit in mice.

This study investigated the effect of the γ-aminobutyric acidB (GABAB) receptor agonist, baclofen, on alcohol deprivation effect (the transient increase in alcohol intake occurring after a period of alcohol abstinence) in Sardinian alcohol-preferring (sP) rats exposed to 4 bottles containing water and 10%, 20%, and 30% (v/v) alcohol, respectively. Acute administration of baclofen (1 mg/kg, i.p.) suppressed both aspects of alcohol deprivation effect: the extra-intake of alcohol and the selection of the highest concentrated alcohol solution. These results suggest that the GABAB receptor is part of the neural substrate mediating alcohol deprivation in sP rats.

Aims: To evaluate the number of subjects with possible alcohol use disorders (SPAUD) among primary care patients in Cagliari, Sardinia, Italy, by means of the self-administration of Alcohol use disorder identification test (AUDIT) and CAGE questionnaires. Methods: 939 patients waiting in 10 surgeries of primary care physicians were asked to take part in the study. A sample of 309 women and 197 men (total 506), aged between 18 and 65 years, agreed to participate and completed both questionnaires. SPAUD were defined as those achieving cut-off scores of 5 for AUDIT and/or 1 for CAGE. Results: Seventy-nine (15.61%) patients were SPAUD, achieving a positive score in at least one questionnaire. Fifty-six (11.07%) and forty-six (9.09%) patients yielded positive results with AUDIT and CAGE, respectively. Twenty-three (4.55%) patients were positive at both AUDIT and CAGE. Significantly higher proportions of men than women were recorded among SPAUD.Conclusions:The results of the present survey indicate a high number of SPAUD in a sample of primary care settings in Cagliari, closely similar to the occurrence of alcohol use disorders estimated in several other community-based primary care clinics in Western Countries.

This chapter describes the clincial experience related to the use of Baclofen as a pharmacological treatment of alcohol withdrawal syndrome.

Previous work indicated that tolerance to the anorectic effect of the cannabinoid CB1 receptor antagonist/inverse agonist, rimonabant, developed rather rapidly in rats and mice given access to a standard rodent chow. The present study was designed to investigate whether the reducing effect of rimonabant on intake of a highly palatable food such as a chocolate-flavoured beverage underwent a development of tolerance as rapid as that manifested on intake of a standard rodent chow. To this aim, Wistar rats were concurrently exposed, with unlimited access for 24 h/day, to the chocolate-flavoured beverage, regular food pellets and water. Rimonabant (0, 1.25, 2.5 and 5 mg/kg; i.p.) was administered once a day for 21 consecutive days. Rimonabant administration resulted in a dose-dependent suppression of the high, daily intake of the chocolate-flavoured beverage; this effect lasted for the entire 21-day treatment period, without any apparent development of tolerance. Conversely, rimonabant-induced reduction in daily intake of regular food pellets was of a smaller magnitude and was limited to the first 3–4 days of treatment. Together, these results indicate that chronically administered rimonabant was more effective and longer-lasting in reducing the intake of a highly palatable food than that of regular food pellets in rats. These results also suggest that rimonabant may be more active on the hedonic rather than nutritive properties of diets.

Study objective Recent reports on fatalities associated with overdoses from 1,4-butanediol (1,4-BD), a precursor of the drug of abuse γ-hydroxybutyric acid (GHB), pose the need for investigations focusing on possible pharmacologic remedies. Accordingly, the present study investigates whether 4-methylpyrazole (4-MP; also termed fomepizole and Antizol), an inhibitor of alcohol dehydrogenase (the enzyme involved in the first step of the conversion of 1,4-BD into GHB), and the γ-aminobutyric acid B (GABA B ) receptor antagonist (2 S )(+)-5,5-dimethyl-2-morpholineacetic acid (SCH 50911), provides protection against 1,4-BD-induced mortality in CD1 mice. Methods Two sets of experiments were conducted with mortality as the outcome measure. In all experiments, mice were initially treated with a lethal dose of 1,4-BD (3 g/kg, intragastric [i.g.]). In the first set of experiments (dose-response curves), once mice had displayed clear signs of 1,4-BD intoxication, animals were randomly allocated in separate groups (n=10) and treated acutely with either 4-MP (vehicle, 3, 10, 30, and 100 mg/kg, intraperitoneal [i.p.]) or SCH 50911 (vehicle, 75, 150, and 300 mg/kg, i.p.). Mortality was recorded every hour for the first 9 hours and 12, 18, and 24 hours after 1,4-BD injection. In the second set of experiments (time course), mice were randomly allocated in separate groups (n=10). A single dose of either 4-MP (30 mg/kg, i.p.) or SCH 50911 (150 mg/kg, i.p.) was administered 15, 30, 60, 90, or 120 minutes after administration of 3 g/kg 1,4-BD (i.g.). Again, mortality was recorded every hour for the first 9 hours and 12, 18, and 24 hours after 1,4-BD injection. Results In the dose-response experiments, the acute administration of 4-MP and SCH 50911 exerted a dose-dependent resuscitative effect in mice acutely intoxicated by 3 g/kg 1,4-BD. Specifically, 30 and 100 mg/kg 4-MP and 150 mg/kg SCH 50911 protected all treated mice against 1,4-BD-induced mortality. Conversely, all mice treated with 4-MP- and SCH 50911-vehicle died. In the time-course experiments, protection induced by 30 mg/kg 4-MP was complete when administered up to 90 minutes after 1,4-BD injection. Vice versa, the complete protection induced by 150 mg/kg SCH 50911 progressively diminished as the time between 1,4-BD and SCH 50911 administration was increased from 15 to 120 minutes. Conclusion These results indicate that both 4-MP and SCH 50911 protected against mortality induced by 1,4-BD. Further, these results suggest that 1,4-BD-induced mortality in mice is a result of conversion of 1,4-BD into GHB and GHB-induced activation of the GABA B receptor. Because both 4-MP and GABA B receptor antagonists are available for human use, clinical studies on their ability to reverse the consequences of 1,4-BD and GHB intoxication, including fatal events, might be considered.

Several lines of evidence indicate that the endogenous cannabinoid system is involved in the pharmacological and behavioural effects of alcohol. The mesolimbic dopaminergic (DA) system and the nucleus accumbens (NAc) process rewarding properties of drugs of abuse, including alcohol and cannabinoids, whereas endocannabinoids in these regions modulate synaptic function and mediate short- and long-term forms of synaptic plasticity.The present study was designed to investigate the contribution of the endogenous cannabinoid system in alcohol electrophysiological effects in the mesolimbic reward circuit.We utilized extracellular single cell recordings from ventral tegmental area (VTA) DA and NAc neurons in anesthetized rats. DA neurons were antidromically identified as projecting to the shell of NAc, whereas NAc putative medium spiny neurons were identified by their evoked responses to basolateral amygdala (BLA) stimulation.Alcohol stimulated firing rate of VTA DA neurons and inhibited BLA-evoked NAc neuron spiking responses. The cannabinoid type-1 receptor (CB1) antagonist rimonabant (SR141716A) fully antagonized alcohol effect in both regions. In the NAc, either inhibition of the major catabolic enzyme of the endocannabinoid anandamide, the fatty-acid amyd hydrolase, with URB597 or a pretreatment with the CB1 receptor agonist WIN55212-2 significantly depressed alcohol-induced effects in the NAc.These results corroborate the notion of the involvement of endocannabinoids and their receptors in the actions of alcohol and highlight the endocannabinoid system as a valuable target in the therapy for alcoholism.

Purpose Benzodiazepines are the drugs of choice in the treatment of alcohol withdrawal syndrome (AWS). Recent data have shown that baclofen may reduce AWS symptoms. At present, no comparative studies between baclofen and any benzodiazepine used in AWS treatment are available. Accordingly, the present study was designed to compare efficacy, tolerability and safety of baclofen versus diazepam in the treatment of AWS. Subjects and methods Thirty-seven patients with AWS were enrolled in the study and randomly divided into 2 groups. Baclofen (30 mg/day for 10 consecutive days) was orally administered to 18 patients (15 males, 3 females; median age: 46.5 years). Diazepam (0.5-0.75 mg/kg/day for 6 consecutive days, tapering the dose by 25% daily from day 7 to day 10) was orally administered to 19 patients (17 men, 2 women; median age: 42.0 years). The Clinical Institute Withdrawal Assessment (CIWA-Ar) was used to evaluate physical symptoms of AWS. Results Both baclofen and diazepam significantly decreased CIWA-Ar score, without significant differences between the 2 treatments. When CIWA-Ar subscales for sweating, tremors, anxiety and agitation were evaluated singly, treatment with baclofen and diazepam resulted in a significant decrease in sweating, tremors and anxiety score, without significant differences between the 2 drug treatments. Both treatments decreased the agitation score, although diazepam was slightly more rapid than baclofen. Conclusion The efficacy of baclofen in treatment of uncomplicated AWS is comparable to that of the "gold standard" diazepam. These results suggest that baclofen may be considered as a new drug for treatment of uncomplicated AWS.

Gamma-hydroxybutyric acid (GHB) and its precursors, 1,4-butanediol (1,4-BD) and gamma-butyrolactone (GBL), are recreational drugs widely abused in the US, Europe and Australasia. A severe withdrawal syndrome from GHB, 1,4-BD and GBL has been increasingly documented over the last years, necessitating the development of a reliable animal model for investigations of potential therapeutic approaches. The present study describes the induction and occurrence of audiogenic seizures as a sign of withdrawal from GHB and 1,4-BD in selectively bred Sardinian alcohol-preferring (sP) rats, treated with escalating doses of GHB (1.5-3.5 g/kg, twice daily; i.g.) or 1,4-BD (500-1000 mg/kg, twice daily; i.g.) for 9 consecutive days. Acute administration of the selective GABA(B) receptor antagonist, SCH 50911, dramatically increased seizure occurrence. We propose that the inherent sensitivity of sP rats to different GHB-associated responses may have contributed to the unraveling of a phenomenon which was otherwise not recognizable in other rat strains.

The present paper synthetically reviews the multiple experimental lines of evidence indicating the ability of the prototypic cannabinoid CB(1) receptor antagonist, rimonabant (also known as SR 141716), to suppress the reinforcing/rewarding properties of different drugs of abuse, including cocaine, heroin, nicotine and alcohol, in laboratory rodents. This paper also reviews the data demonstrating that rimonabant reduces food intake and body weight in laboratory animals and humans. Taken together, the data reviewed here suggest that rimonabant may constitute a new and potentially effective medication for the treatment of drug addiction and obesity-related disorders.

Aims: The present study investigated the effect of the newly synthesized cannabinoid CB1 receptor antagonist, SR147778, on alcohol intake and the motivational properties of alcohol in selectively bred Sardinian alcohol-preferring (sP) rats. Methods and Results: In Experiment 1, the repeated administration of SR147778 (0.3–3 mg/kg twice daily, i.p.) specifically suppressed the acquisition of alcohol drinking behaviour in alcohol-naive rats exposed to the two-bottle ‘alcohol vs water’ choice regimen for 24 h/day. In Experiment 2, an acute administration of SR147778 (2.5–10 mg/kg, i.p.) specifically reduced alcohol intake in alcohol-experienced rats that were given alcohol and water under the two-bottle choice regimen in daily sessions of 4 h. In Experiment 3, an acute administration of SR147778 (0.3–3 mg/kg, i.p.) suppressed the ‘alcohol deprivation effect’, i.e. the extra-intake of alcohol occurring after a period of alcohol abstinence. In Experiment 4, an acute administration of SR147778 (0.3–3 mg/kg, i.p.) specifically suppressed the extinction responding for alcohol, i.e. the maximal number of lever responses reached in the absence of alcohol in rats trained to lever-press for alcohol (measure of the motivational properties of alcohol). In Experiment 5, the combination of 3 mg/kg of SR147778 (i.p.) and 0.5 g/kg of alcohol (i.p.), a dose comparable with those usually consumed by sP rats in each drinking binge, failed to induce any conditioned taste aversion. Conclusion: Taken together, these results extend to SR147778 the anti-alcohol profile of the prototype cannabinoid CB1 receptor antagonist, rimonabant (SR141716), and strengthen the hypothesis that the cannabinoid CB1 receptor is part of the neural substrate mediating alcohol intake and the motivational properties of alcohol. ( Received 30 July 2004; first review notified 1 September 2004; in revised form 14 September 2004; accepted 1 October 2004 )

Chronic treatment of mice with the specific γ-aminobutyric acid B (GABA B ) receptor antagonist (2 S )(+)-5,5-dimethyl-2-morpholineacetic acid (SCH 50,911) increased both the number of GABA B receptors in the whole brain (measured as [ 3 H]CGP 54626 [ S -( R , R )]-3-[[1-(3,4-dichlorophenyl)amino]-2-hydroxypropyl](cyclohexylmethyl)phosphinic acid hydrochloride binding) and the ability of baclofen to activate GABA B receptor coupled G-protein (measured as % reduction of the EC 50 of baclofen to activate [ 35 S]GTPγS binding). The results indicate that persistent blockade of GABA B receptors leads to their compensatory up-regulation and suggest that GABA B receptors are tonically activated by endogenous GABA.

The present study investigated whether the differential sensitivity of selectively bred γ-hydroxybutyric acid (GHB)-sensitive (GHB-S) and GHB-resistant (GHB-R) rats to GHB- and baclofen-induced sedation/hypnosis generalized to the motor incoordinating effect of the two drugs. To this aim, GHB-S and GHB-R rats were tested on a Rota-Rod after the acute administration of GHB (100–500 mg/kg, i.p.) and baclofen (1.25–5 mg/kg, i.p.). Significant line differences were observed in the dose–response curves for both GHB and baclofen, with GHB-S rats displaying a greater sensitivity to the motor incoordinating effects of both drugs than GHB-R rats. No line difference was observed in diazepam (1.25–5 mg/kg, i.p.), pentobarbital (5–15 mg/kg, i.p.), and ethanol (1–1.5 g/kg, i.p.) dose–response curves. These results suggest that the differential sensitivity of GHB-S and GHB-R rats to GHB and baclofen extends to the effects produced by doses of the two drugs which are 5–10 times lower than those for which rats have been selectively bred. These results are discussed in terms of the GABAB receptor being the likely neural substrate on which the differential sensitivity of GHB-S and GHB-R rats resides.

In the rat brain, gamma-hydroxybutyric-acid (GHB) increases the concentrations of 3alpha-hydroxy,5alpha-pregnan-20-one (allopregnanolone, 3alpha,5alpha-THP) and 3alpha,21-dihydroxy,5alpha-pregnan-20-one (allotetrahydrodeoxycorticosterone/3alpha,5alphaTHDOC), two neurosteroids acting as positive allosteric modulators of gamma-aminobutyric acid (GABA)(A) receptors. This study was aimed at assessing whether neurosteroids play a role in GHB-induced loss of righting reflex (LORR). Basal and GHB-stimulated brain concentrations of endogenous 3alpha,5alpha-THP and 3alpha,5alpha-THDOC were analyzed in two rat lines, GHB-sensitive (GHB-S) and GHB-resistant (GHB-R), selectively bred for opposite sensitivity to GHB-induced sedation/hypnosis. Basal neurosteroid concentrations were similar in brain cortex of the two rat lines. However, in male GHB-S rats, administration of GHB (1000 mg/kg, i.p., 30 min) increased brain cortical concentrations of 3alpha,5alpha-THP and 3alpha,5alpha-THDOC 7- and 2.5-fold, respectively, whilst male GHB-R animals displayed only a 4- and 2-fold increase, respectively. In GHB-S rats this increase lasted up to 90 min and declined 180 min following GHB administration, a time course that matches LORR onset and duration. In contrast, in GHB-R rats, which failed to show GHB-induced LORR, brain cortical 3alpha,5alpha-THP and 3alpha,5alpha-THDOC had returned to control values within 90 min. At onset of LORR, a similar increase in brain cortical levels of 3alpha,5alpha-THP and 3alpha,5alpha-THDOC (2-3-fold) was observed in GHB-S female rats and in the few female GHB-R rats that lost the righting reflex after GHB administration, but not in female GHB-R rats failing to show LORR. Sub-hypnotic doses (7.5 and 12.5 mg/kg, i.p.) of pregnanolone, administered 10 min before GHB, dose-dependently facilitated the expression of GHB-induced LORR in GHB-R male rats. These results suggest that the GHB-induced increases of brain 3alpha,5alpha-THP and 3alpha,5alpha-THDOC concentrations are implicated in the eliciting of the sedative/hypnotic action of GHB.

The present study was aimed at assessing the in vivo effectiveness of the positive allosteric modulator of the gamma-aminobutyric acidB (GABAB) receptor, CGP7930 [2,6-di-tert-butyl-4-(3-hydroxy-2,2-dimethyl-propyl)-phenol]. The synergistic potentiation of GABAB receptor functioning, previously observed in different in vitro assays, has been confirmed in the present work, where pretreatment with CGP7930 (10-170 mg/kg, i.p.) resulted in a marked potentiation of the sedative/hypnotic effect of the GABAB receptor agonists, baclofen (40 mg/kg, i.p.) and gamma-hydroxybutyric acid (500 mg/kg, i.p.), in DBA mice. Pretreatment with the GABAB receptor antagonist, SCH 50911 [(S)-5,5-dimethyl-2-morpholine acetic acid; 100 mg/kg, i.p.], resulted in a complete blockade of the sedative/hypnotic effect of the combination of CGP7930 with either baclofen or gamma-hydroxybutyric acid. These results confirm that CGP7930 may constitute an interesting tool for pharmacological studies in the GABAB receptor field.

Although substantial evidence has shown interactions between glutamatergic and dopaminergic systems play a cardinal role in the regulation of attentional processes, their involvement in informational filtering has been poorly investigated. Chiefly, little research has focused on functional correlations between the dopaminergic system and the mechanism of action of N-methyl-D-aspartate (NMDA) receptor antagonists on sensorimotor gating. The present study was targeted at evaluating whether the activation of D1 and D2 receptors is able to interact with the disruption of prepulse inhibition (PPI) of startle mediated by dizocilpine, a selective, noncompetitive NMDA receptor antagonist. We tested the effects of SKF 38393 ((+/-)-1-phenyl-2,3,4,5-tetrahydro-(1H)-3-benzazepine-7,8-diol) (10 mg/kg, s.c.), a selective D1 agonist, and quinpirole (0.3, 0.6 mg/kg, s.c.), a D2 agonist, in rats, per se and in cotreatment with different doses of dizocilpine, ranging from 0.0015 to 0.15 mg/kg (s.c.). Subsequently, the effect of the D1 antagonist SCH 23390 ((R)-(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine) (0.05, 0.1 mg/kg, s.c.) on PPI disruptions mediated by dizocilpine and by combination of dizocilpine and SKF 38393 was tested. Two further experiments were performed to verify whether the synergic effect of the D1 agonist with dizocilpine was counteracted by effective doses of haloperidol (0.1, 0.5 mg/kg, i.p.) and clozapine (5, 10 mg/kg, i.p.). All experiments were carried out using standard procedures for the assessment of PPI of the acoustic startle reflex. SKF 38393, while unable to impair sensorimotor gating alone, induced PPI disruption in cotreatment with 0.05 and 0.15 mg/kg of dizocilpine, both ineffective per se. Furthermore, this effect was reversed by SCH 23390, but not by haloperidol or clozapine. Conversely, no synergistic effect was exhibited between quinpirole and dizocilpine, at any given dose. These findings suggest that D1, but not D2 receptors, enhance the disruptive effect of dizocilpine on PPI.

The present paper describes the results of recent pharmacological studies implicating the cannabinoid CB1 receptor in the neural circuitry regulating alcohol consumption and motivation to consume alcohol. Cannabinoid CB1 receptor agonists have been found to specifically stimulate alcohol intake and alcohol's motivational properties in rats. Conversely, the cannabinoid CB1 receptor antagonist, SR 141716, has been reported to specifically suppress acquisition and maintenance of alcohol drinking behavior, relapse-like drinking and alcohol's motivational properties in rats. More recent data indicate that opioid receptor antagonists a) blocked the stimulatory effect of cannabinoids on alcohol intake, and b) synergistically potentiated the suppressing effect of SR 141716 on alcohol intake and alcohol's motivational properties. Consistently, SR 141716 blocked the stimulatory effect of morphine on alcohol intake. These results suggest a) the existence of a functional link between the cannabinoid and opioid receptor systems in the control of alcohol intake and motivation to consume alcohol, and b) that novel and potentially effective therapeutic strategies for alcoholism may come from the combination of cannabinoid and opioid receptor antagonists.

Administration of morphine and cannabinoids stimulates alcohol intake in rats. The present study investigated whether the promoting effect of morphine and of the cannabinoid receptor agonist, WIN 55,212-2 [(R)-(+)-[2,3-dihydro-5-methyl-3-(4-morpholinylmethyl)pyrrolo[1,2,3-de]-1,4-benzoxazin-6-yl]-1-naphthalenylmethanone], on alcohol intake was prevented by the gamma-aminobutyric (GABA)(B) receptor agonist, baclofen. Sardinian alcohol-preferring (sP) rats were given alcohol (10%, v/v) and water under the standard homecage two-bottle-free choice regimen with unlimited access for 24 h/day. Baclofen (0, 0.5 and 1 mg/kg; i.p.) was administered acutely 30 min before lights off. Morphine (0 and 1 mg/kg, s.c.) or WIN 55,212-2 (0 and 2 mg/kg, i.p.) was administered acutely 10 min after baclofen. Alcohol intake was recorded 60 min after lights off. As predicted, both morphine and WIN 55,212-2 produced a specific and marked increase in alcohol intake. Pretreatment with baclofen, which failed to alter alcohol intake when given alone, dose-dependently suppressed morphine- and WIN 55,212-2-induced promotion of alcohol drinking. These results suggest the involvement of the GABA(B) receptor in the neural circuitry mediating the stimulating effect of morphine and cannabinoids on alcohol consumption in sP rats.

Background Recent studies have raised concerns about subtle long-lasting neurobiological changes that might be triggered by exposure to Cannabis derivatives, especially in a critical phase of brain maturation, such as puberty. The mesolimbic dopamine (DA) system, involved in the processing of drug-induced reward, is a locus of action of cannabinoids and endocannabinoids. Thus, we compared the effects of repeated cannabinoid administration in adolescent and adult rats on DA neuronal functions and responses to drugs of abuse. Methods Single-unit extracellular recordings from antidromically identified mesoaccumbens DA neurons and from their target cells in the nucleus accumbens were carried out in urethane-anesthetized rats. Animals were pretreated during adolescence or adulthood, for 3 days, with the cannabinoid agonist WIN55212.2 (WIN) or vehicle and allowed a 2-week interval. Results In cannabinoid-administered rats, DA neurons were significantly less responsive to the stimulating action of WIN, regardless of the age of pretreatment; however, in the adolescent group, but not in the adult, long-lasting cross-tolerance developed to morphine, cocaine, and amphetamine. Conclusions Our study suggests that an enduring form of neuronal adaptation occurs in DA neurons after subchronic cannabinoid intake at a young age, affecting subsequent responses to drugs of abuse.

A recent in-vitro study demonstrated that the potent disulfide reducing agent, DL-dithiothreitol (DTT), may alter the structural stability of the GABA(B) receptor, probably inactivating the disulfide bonds between four cysteine residues located in the GABA(B1(a)) receptor structure.The present study was designed to evaluate whether DTT treatment was capable of antagonizing some behavioral effects of pharmacological stimulation of the GABA(B) receptor.Experiments on sedation/hypnosis induced by the GABA(B) receptor agonists baclofen, SKF 97541, CGP 44532 and gamma-hydroxybutyric acid (GHB) in DBA mice and selectively bred GHB-sensitive (GHB-S) rats, and a GHB drug discrimination study in Long Evans rats were conducted. Specificity of the DTT action on the GABA(B) receptor was investigated by assessing its effect on the sedative/hypnotic effect induced by diazepam, ketamine and ethanol.DTT prevented the sedative/hypnotic effect of all GABA(B) receptor agonists tested and also reversed baclofen-induced sedation/hypnosis. In contrast, DTT had no effect on, or even potentiated, sedation/hypnosis produced by diazepam, ketamine or ethanol. DTT completely blocked the discriminative stimulus effects of GHB.These results are discussed in terms of DTT altering the stability of the binding domain of the GABA(B) receptor, hindering the drug-receptor interaction.

The cannabinoid CB(1) receptor antagonist, SR 141716 (Rimonabant), has been reported to stimulate, when acutely administered, intestinal motility in mice. The present study was aimed at determining whether tolerance develops to its repeated administration. Mice were treated twice a day for up to 8 consecutive days with 0, 3 and 5.6 mg/kg SR 141716 (i.p.). On days 1, 3, 5 and 8, separate groups of mice were treated intragastrically with a non-absorbable colored marker (carmine). The distance traveled by the head of the marker in the small intestine was recorded. On day 1, SR 141716 markedly activated intestinal peristalsis, but complete tolerance to this effect developed within the third day of treatment. The results may have some relevance to the proposed future clinical use of SR 141716.

Administration of the cannabinoid CB(1) receptor antagonist, SR 141716 [N-piperidino-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-3-pyrazole-carboxamide], has been reported to reduce alcohol intake and alcohol self-administration in different models of excessive alcohol consumption, including the selectively bred Sardinian alcohol-preferring (sP) rats. The present study investigated whether SR 141716 was also capable of decreasing, in this rat line, alcohol's motivational properties. Extinction responding for alcohol, defined as the maximal number of lever responses reached in the absence of alcohol in rats trained to lever-press for alcohol, was used as index of alcohol's motivational properties. Rats were initially trained to lever-press for oral alcohol (15%, v/v) under a fixed ratio (FR) schedule of FR4. Once self-administration behavior was established, extinction sessions were conducted. SR 141716 (0, 0.3, 1 and 3 mg/kg; i.p.) was acutely administered before extinction sessions. In order to assess the specificity of SR 141716 action on extinction responding for alcohol, a separate group of sP rats was trained to lever-press for a 3% (w/v) sucrose solution under an FR4 schedule. SR 141716 administration produced a dose-dependent, virtually complete suppression of extinction responding for alcohol. In contrast, extinction responding for sucrose was not significantly altered by treatment with SR 141716. Further to the consummatory aspects, these results also extend the suppressing effect of SR 141716 to the appetitive aspects of alcohol drinking behavior in sP rats. The results also implicate the cannabinoid CB1 receptor in the neural substrate mediating alcohol's motivational properties in this rat line.

A growing evidentiary body indicates cannabinoid exposure is conducive to cognitive impairment and psychotic phenomena in vulnerable individuals. In this respect, recent studies have displayed controversial results on the ability of cannabinoids to elicit sensorimotor gating alterations and attentional filtering, whose disruption is a distinctive feature of psychosis. The goal of this study was to investigate the effects of acute, subchronic, and chronic treatment with the synthetic CB receptor agonist WIN 55,212-2 (WIN) on prepulse inhibition (PPI) of the acoustic startle reflex (ASR), a powerful paradigm for evaluation of sensorimotor gating. Different groups of adult Sprague-Dawley rats were treated with 0.5, 1, and 2 mg/kg WIN (i.p.) acutely, as well as for 7 days and 21 days. All animals underwent testing 40 min after the last treatment and their evaluation was compared with that of animals treated with vehicle. In a separate group, the effects of WIN withdrawal were also analyzed, 24 h after discontinuation of a 21-day treatment. No variation in PPI was detected in any of the test groups when compared with controls, whatever the dosage and the treatment. These findings suggest WIN does not impair sensorimotor gating in Sprague-Dawley rats and confirm clinical evidence according to which cannabis is an unlikely causative of psychosis among non-vulnerable individuals. Nonetheless, since in other studies the same compound was shown to induce PPI alterations in Wistar rats, our results are also suggestive that genetic differences might be critical for the development of cannabis-induced cognitive disorders.

Cannabinoid receptors have been studied extensively in view of their potential functional role in several physiological and pathological processes. For this reason, the search for new potent, selective ligands for subtype CB receptors, CB(1) and CB(2), is still of great importance, in order to investigate their role in various physiological functions. The present study describes the synthesis and the biological properties of a series of 1,8-naphthyridine derivatives, characterised by the presence of some important structural requirements exhibited by other classes of cannabinoid ligands, such as an aliphatic or aromatic carboxamide group in position 3, and an alkyl or arylalkyl substituent in position 1. These compounds were assayed for binding both to the brain and to peripheral cannabinoid receptors (CB(1) and CB(2)). The results obtained indicate that the naphthyridine derivatives examined possess a greater affinity for the CB(2) receptor than for the CB(1) receptor. In particular, derivatives 6a and 7a possess an appreciable affinity for the CB(2) receptor, with K(i) values of 5.5 and 8.0 nM respectively; also compounds 4a, 5a and 8a exhibit a good CB(2) affinity, with K(i) values in the range of 10-44 nM. Furthermore, compounds 3g-i and 18 revealed a good CB(2) selectivity, with a CB(1)/CB(2) ratio >20.

Results of a recent investigation revealed that selectively bred Indiana ethanol-nonpreferring (NP) rats could be “environmentally” conditioned to consume high amounts of ethanol. Specifically, a long-term exposure to a sucrose-plus-ethanol solution resulted, when sucrose was faded out, in an ethanol intake that was equivalent to that recorded in the counterpart ethanol-preferring (P) rats. The current study was designed to extend the above investigation to the selectively bred Sardinian alcohol-nonpreferring (sNP) rats. To this aim, rats of the sNP and Sardinian alcohol-preferring (sP) lines were exposed to a 108-day sucrose-fading procedure, which was virtually identical to that previously used with NP and P rats. Results indicated that intake of the sucrose-plus-ethanol solution in sNP rats was maintained predominantly by sucrose, as negligible intakes of ethanol were observed when sucrose was faded out. In contrast, sP rats maintained high levels of ethanol intake both during and after the induction procedure. These results support the suggestion that an environmental manipulation such as a long-term exposure to a sucrose-fading procedure did not overcome the genetically determined predisposition to avoid ethanol in sNP rats.

Results of a recent study have demonstrated that exposure to multiple ethanol concentrations and repeated ethanol deprivation periods in Indiana ethanol-preferring (P) rats resulted in the development of an alcohol deprivation effect (ADE; the temporary increase in voluntary ethanol intake after a period of deprivation from ethanol) characterized by consumption of intoxicating amounts of ethanol. The current study was designed to possibly extend these results to Sardinian alcohol-preferring (sP) rats, generated with the same selective program previously used for P rats. To this aim, ethanol-naive sP rats were exposed initially to the home cage four-bottle choice [10%, 20%, and 30% (vol./vol.) ethanol solutions and water] for eight consecutive weeks. Subsequently, rats were divided into two groups: The first group had continuous access to the four-bottle regimen (nondeprived rats), and the second group was exposed to five cycles of 14-day periods of deprivation from ethanol and 14-day periods of reexposure to the four-bottle regimen. An ADE developed after each deprivation period. However, the extra intake of ethanol was limited to the first hour of each reaccess period. Magnitude of ADE did not change with repeated periods of deprivation. However, a shift in preference toward the two highest concentrations of ethanol solutions was evident from the first reexposure to ethanol and was maintained throughout the study. These results provide further evidence on the heterogeneity of ethanol-drinking behavior among rat lines selectively bred for high ethanol preference and consumption.

A previous study demonstrated that an extract of Salvia miltiorrhiza, a medicinal herb highly valued in Chinese folk medicine for the treatment of different pathologies, including insomnia, was capable of reducing voluntary alcohol intake in selectively bred Sardinian alcohol-preferring (sP) rats. The present study was designed to evaluate the suitability of different emulsifying, suspending agents and solvents as vehicles through which Salvia miltiorrhiza extracts can exert their reducing effect on alcohol intake. A single dose (100 mg/kg) of a standardised extract of Salvia miltiorrhiza was dissolved in either pure Polysorbate 80, arachis oil, PEG 400, or Polyoxyl 35 castor oil, or suspended in 0.5% CMC in water, and administered acutely by gavage to sP rats. A significant and specific reduction in alcohol intake was recorded only in rats treated with the combination of Polysorbate 80 plus the Salvia miltiorrhiza extract. A further experiment demonstrated that the ability of the combination of Polysorbate 80 in water plus the Salvia miltiorrhiza extract to decrease alcohol intake was dependent upon the concentration of Polysorbate 80. The results of the present study demonstrate that Polysorbate 80 is a proper vehicle for unravelling the reducing effect of Salvia miltiorrhiza extracts on alcohol intake. The ability of Polysorbate 80 to form micelles with the active ingredient(s) of the Salvia miltiorrhiza may explain these results. They may also offer relevant information for pharmaceutical preparation of Salvia miltiorrhiza extract to be used in future clinical trials.

Since baclofen, the prototypical GABA(B) receptor agonist, is known to reduce the activity of dopaminergic mesolimbic neurons, a putative antipsychotic property of this compound has been suggested, but the evidence for this is still controversial.The aim of the present study was to elucidate the effects of baclofen on the prepulse inhibition (PPI) of the acoustic startle response (ASR), a behavioral paradigm considered to be one of the most powerful tools for the evaluation of sensorimotor gating and for the screening of antipsychotics.We tested the effects of baclofen (1.25, 2.5, 5 and 10 mg/kg IP) in rats, per se and in co-treatment with some of the substances known to induce a robust reduction of PPI, such as apomorphine (0.25 mg/kg SC) and dizocilpine (0.1 mg/kg SC). Finally, in order to ascertain whether the effects of baclofen could be ascribed to its activity on GABA(B) receptors, we analyzed whether its action could be prevented by pretreatment with SCH 50911, a selective GABA(B) receptor antagonist (20 mg/kg IP). All the experiments were carried out using standard procedures for the assessment of PPI of the ASR.Baclofen per se produced no significant change in PPI parameters. Moreover, while no effect on apomorphine-mediated alterations in PPI parameters was observed, baclofen proved able to reverse dizocilpine-induced PPI disruption, and this effect was significantly prevented by SCH 50911. On the other hand, this last compound exhibited no effects per se at the same dose.These results indicate that GABA(B) receptors are implicated in the neurobiological circuitry accounting for glutamatergic action in sensorimotor gating, and therefore can be proposed as putative new targets in the pharmacological therapy of psychotic disorders. Further studies should be addressed to evaluate more closely the clinical efficacy of baclofen in this respect.

Sardinian alcohol non-preferring (sNP) rats, selected for their low ethanol preference and consumption, carry a point mutation (R100Q) in the gene coding for GABA(A) receptor alpha(6) subunit, which becomes more sensitive to diazepam-evoked GABA currents. We performed binding studies in the cerebellum of normal (RR) and mutated (QQ) sNP rats using [3H]Ro 15-4513, an inverse agonist for the benzodiazepine site which binds both diazepam insensitive and diazepam sensitive sites. Saturation curves performed on cerebellar membrane from genotyped rats indicated an higher affinity of [3H]Ro 15-4513 for GABA(A) receptors in QQ with respect to RR rats (K(d) values 4.0+/-0.67 and 6.24+/-0.95 nM, respectively), with similar B(max) values (3.5+/-0.25 and 3.9+/-0.39 pmol/mg protein, respectively). Diazepam displacement curves showed a two component model for both genotypes, with similar K(i1) values for QQ and RR (3.6+/-0.62 and 4.9+/-0.33 nM, respectively). In QQ rats diazepam is able to completely displace [3H]Ro 15-4513 (K(i2)=1.48+/-0.27 microM), while in RR rats the diazepam sensitive sites are still present (K(i2)10 microM). The basal mRNA and protein expression level of the alpha(6) subunit were similar in RR and QQ rats. The electrophysiological profile of oocytes of Xenopus laevis injected with cerebellar synaptosomes showed that ethanol positively modulated GABA-evoked currents significantly more in QQ than in RR rats. These data contribute to the characterization of the function of GABA(A) alpha(6) subunit and its involvement in determining alcohol related behavior.