Tag Archives: CB1

Blockade of the cannabinoid CB1 receptor and alcohol dependence: preclinical evidence and preliminary clinical data.

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Abstract

“The present paper summarizes the results of a number of pharmacological studies implicating the cannabinoid CB(1) receptor in the neural circuitry regulating different alcohol-related behaviors in rodents. Specifically, cannabinoid CB(1) receptor antagonists–including the prototype, rimonabant–have been reported to suppress: (a) acquisition and maintenance of alcohol drinking behavior under the 2-bottle “alcohol vs water” choice regimen; (b) the increase in alcohol intake occurring after a period of alcohol abstinence (an experimental model of alcohol relapse); (c) alcohol’s reinforcing and motivational properties measured in rats trained to perform a specific task (e.g., lever-pressing) to access alcohol; (d) reinstatement of extinguished alcohol-seeking behavior triggered in rats by a nicotine challenge or presentation of cues previously associated to alcohol availability (another model of alcohol relapse). Additional data indicate that the opioid receptor antagonists, naloxone and naltrexone, synergistically potentiate the suppressing effect of rimonabant on alcohol intake and alcohol’s motivational properties in rats. Conversely, the two clinical studies conducted to date (one in alcohol-dependent individuals and one in nontreatment-seeking heavy alcohol drinkers) yielded less conclusive results. Unfortunately, the recent discontinuation–due to the occurrence of some psychiatric adverse effects–of all trials with cannabinoid CB(1) receptor antagonists apparently hinders further investigations on the potential of rimonabant in the treatment of alcohol dependence.”

http://www.ncbi.nlm.nih.gov/pubmed/20201816

Cannabinoid receptor 1 blocker rimonabant (SR 141716) for treatment of alcohol dependence: results from a placebo-controlled, double-blind trial.

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Abstract

“Multiple lines of evidence suggest that the endocannabinoid system is implicated in the development of alcohol dependence. In addition, in animal models, the cannabinoid receptor 1 blocker rimonabant was found to decrease alcohol consumption, possibly by indirect modulation of dopaminergic neurotransmission. This was a 12-week double-blind, placebo-controlled, proof-of-concept study to assess the possible efficacy of the cannabinoid receptor 1 antagonist rimonabant 20 mg/d (2 x 10 mg) in the prevention of relapse to alcohol in recently detoxified alcohol-dependent patients. A total of 260 patients were included, 258 were exposed to medication, and 208 (80.6%) were men. Patients had an alcohol history of 15 years on average. More patients in the rimonabant group (94/131 [71.8%]) completed treatment compared with the placebo group (79/127 [62.2%]). Although there was a modest effect of rimonabant with respect to relapse rate, there were no statistically significant differences between treatment groups. Approximately 41.5% of the rimonabant group had relapsed to drinking at the end of the study compared with 47.7% of the placebo group (obtained from Kaplan-Meier-curve). Differences were more marked but not statistically significant in patients who relapsed to heavy drinking: 27.7% versus 35.6%, respectively. Safety and tolerance of the drug were good. Similar rates of adverse events were reported between the 2 groups; less patients experienced serious events or discontinued the treatment with rimonabant compared with placebo. Rates of depression-related events were low (3.8% with rimonabant compared with 1.6% with placebo). Patients on rimonabant lost weight (Mean, -1.7 kg) compared with baseline, whereas there was no such change in the placebo group. Weight loss was more pronounced in patients with a higher body mass index. In addition, there was a significant decrease in leptin levels in the rimonabant group compared with baseline. Lack of efficacy in this study may be explained by a very high response rate in the placebo group and a relatively short treatment duration. Taking the substantial numbers of animal studies suggesting a possible role of CB1 antagonists for the treatment of alcohol dependence into account, it seems worthwhile to further test cannabinoid blockers in the treatment of alcoholism.”

http://www.ncbi.nlm.nih.gov/pubmed/18480689

Positron Emission Tomography Shows Elevated Cannabinoid CB (1) Receptor Binding in Men with Alcohol Dependence.

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Abstract

“BACKGROUND:

Several lines of evidence link cannabinoid (CB) type 1 (CB (1) ) receptor-mediated endogenous CB (eCB) signaling to the etiology of alcohol dependence (AD). However, to date, only peripheral measures of eCB function have been collected in living humans with AD and no human in vivo data on the potentially critical role of the brain CB (1) receptor in AD have been published. This is an important gap in the literature, because recent therapeutic developments suggest that these receptors could be targeted for the treatment for AD.”

 

“CONCLUSIONS:

These findings agree with preclinical evidence and provide the first, albeit still preliminary in vivo evidence suggesting a role for brain CB (1) receptors in AD. The current study design does not answer the important question of whether elevated CB (1) receptors are a preexisting vulnerability factor for AD or whether elevations develop as a consequence of AD.”

http://www.ncbi.nlm.nih.gov/pubmed/22551199

Reduced cannabinoid CB(1) receptor binding in alcohol dependence measured with positron emission tomography.

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Abstract

“Brain cannabinoid CB(1) receptors contribute to alcohol-related behaviors in experimental animals, but their potential role in humans with alcohol dependence is poorly understood. We measured CB(1) receptors in alcohol dependent patients in early and protracted abstinence, and in comparison with control subjects without alcohol use disorders, using positron emission tomography and [(18)F]FMPEP-d(2), a radioligand for CB(1) receptors. We scanned 18 male in-patients with alcohol dependence twice, within 3-7 days of admission from ongoing drinking, and after 2-4 weeks of supervised abstinence. Imaging data were compared with those from 19 age-matched healthy male control subjects. Data were also analyzed for potential influence of a common functional variation (rs2023239) in the CB(1) receptor gene (CNR1) that may moderate CB(1) receptor density. On the first scan, CB(1) receptor binding was 20-30% lower in patients with alcohol dependence than in control subjects in all brain regions and was negatively correlated with years of alcohol abuse. After 2-4 weeks of abstinence, CB(1) receptor binding remained similarly reduced in these patients. Irrespective of the diagnostic status, C allele carriers at rs2023239 had higher CB(1) receptor binding compared with non-carriers. Alcohol dependence is associated with a widespread reduction of cannabinoid CB(1) receptor binding in the human brain and this reduction persists at least 2-4 weeks into abstinence. The correlation of reduced binding with years of alcohol abuse suggests an involvement of CB(1) receptors in alcohol dependence in humans.”

http://www.ncbi.nlm.nih.gov/pubmed/22776901

A Critical Role for the Cannabinoid CB1 Receptors in Alcohol Dependence and Stress-Stimulated Ethanol Drinking

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“Although many people drink alcohol regularly, only some become addicted. Several studies have shown that genetic and environmental factors contribute to individual differences in the vulnerability to the effects of alcohol. Among the environmental factors, stress is perhaps the most important trigger for relapse after a period of abstinence. Here we show that ethanol withdrawal symptoms were completely absent in cannabinoid CB1 receptor-deficient mice, although acute effects of ethanol and ethanol tolerance and preference were basically normal. Furthermore, foot-shock stress had no affect on alcohol preference in Cnr1−/− mice, although it induced a dramatic increase in Cnr1+/+ animals. These results reveal a critical role for the CB1 receptor in clinically important aspects of alcohol dependence and provide a rationale for the use of CB1 receptor antagonists in the treatment of alcohol addiction.”

“In summary, the endocannabinoid system does not seem to be crucial for the rewarding effects of ethanol and the manifestation of normal ethanol drinking behaviors. However, it appears to play an important role in the manifestation of stress-induced alcohol drinking and ethanol withdrawal. These results support the notion that the neuronal mechanisms involved in drug reinforcement are dissociable from those involved in withdrawal and reinstatement. Indeed, our results demonstrate that ethanol tolerance and physical dependence can be separated. Thus, CB1 receptor antagonists may be useful for the treatment of alcohol addiction.”

http://www.jneurosci.org/content/23/6/2453.long

Cannabinoid receptor 1 gene is associated with alcohol dependence.

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Abstract

“BACKGROUND:

Alcohol dependence (AD) vulnerability is determined by a complex array of genetic factors. Given the potential role of endocannabinoid system in AD, polymorphisms within cannabinoid receptor 1 gene (CNR1) have been potentially associated with susceptibility to this disease. We thus aimed to examine the relationship between 3 allelic variants of CNR1 (rs6454674, rs1049353, and rs806368) and AD.

METHODS:

Genotyping of the aforementioned polymorphisms was carried out by PCR in 298 male alcoholics (187 of them with AD) and 155 healthy controls. Single-marker, haplotype, and interaction analysis were performed to analyze the influence of CNR1 gene on AD susceptibility.

RESULTS:

We found an association between CNR1 gene and AD after haplotype analysis. Alcoholic patients with TGT haplotype (corresponding to rs6454674-rs1049353-rs806368 polymorphisms in this order) were less prone to have AD (p = 0.017). Besides, alcoholics with a G/T substitution of the first marker (GGT haplotype) or a C/T substitution of the third marker (TGC haplotype) were more likely to develop AD (p = 0.006 and 0.004, respectively) and an interaction was found between the G allele of rs6454674 single nucleotide polymorphism (SNP) and the C allele of rs806368 SNP (p = 0.009).

CONCLUSIONS:

Our findings support previously reported associations of CNR1 with dependence to alcohol and other substances and emphasizes the relevance of endocannabinoid system in AD.”

http://www.ncbi.nlm.nih.gov/pubmed/22085192

[The role of the cannabinoid system in the pathogenesis and treatment of alcohol dependence].

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Abstract

“The lack of satisfactory results of alcohol dependence treatment force us to search for new directions of research. Recent studies concentrate on endocannabinoid transmission. The results show an interplay between the endocannabinoid and dopaminergic signaling in activation of the limbic reward system. The mechanisms leading to development of dependence are very complex and poorly recognized. Endogenous cannabinoids seem to have an important role in the functioning of this system, both directly and indirectly affecting the level of different neurotransmitters. The effect of alcohol on the endocannabinoid system is also complex and involves changes at the molecular level. Experimental studies have demonstrated an important role of the CB1 receptors in the neurochemical mechanism of alcohol consumption and its regulation. SR141716 (rimonabant), a CB1 receptor antagonist, significantly lowers voluntary alcohol intake and motivation for its consumption in various experimental studies. Very encouraging results of preclinical studies were not completely confirmed in the clinical studies. However, further clinical studies are still necessary.”

http://www.ncbi.nlm.nih.gov/pubmed/21934185

Endocannabinoid system and alcohol addiction: pharmacological studies.

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Abstract

“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.”

http://www.ncbi.nlm.nih.gov/pubmed/15939463

Role of endocannabinoids and cannabinoid CB1 receptors in alcohol-related behaviors.

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Abstract

“This review presents the remarkable research during the past several years indicating that some of the pharmacological and behavioral effects of alcohol, including alcohol drinking and alcohol-preferring behavior, are mediated through one of the most abundant neurochemical systems in the central nervous system, the endocannabinoid signaling system. The advances, with the discovery of specific receptors and the existence of naturally occurring cannabis-like substances in the mammalian system and brain, have helped in understanding the neurobiological basis for drugs of abuse, including alcoholism. The cDNA and genomic sequences encoding G-protein-coupled cannabinoid receptors (CB1 and CB2) from several species have now been cloned. This has facilitated discoveries of endogenous ligands (endocannabinoids). To date, two fatty acid derivatives characterized to be arachidonylethanolamide and 2-arachidonylglycerol have been isolated from both nervous and peripheral tissues. Both these compounds have been shown to mimic the pharmacological and behavioral effects of Delta9-tetrahydrocannabinol, the psychoactive component of marijuana. The involvement of the endocannabinoid signaling system in tolerance development to drugs of abuse, including alcohol, were unknown until recently. Studies from our laboratory demonstrated for the first time the downregulation of CB1 receptor function and its signal transduction by chronic alcohol. The observed downregulation of CB1 receptor binding and its signal transduction results from the persistent stimulation of receptors by the endogenous CB1 receptor agonists arachidonylethanolamide and 2-arachidonylglycerol, the synthesis of which is increased by chronic alcohol treatment. The deletion of CB1 receptor has recently been shown to block voluntary alcohol intake in mice, which is consistent with our previous findings where the DBA/2 mice known to avoid alcohol intake had significantly reduced brain CB1 receptor function. These findings suggest a role for the CB1 receptor gene in excessive alcohol drinking behavior and development of alcoholism. Ongoing investigations may lead to the development of potential therapeutic agents to modulate the endocannabinoid signaling system, which will be helpful for the treatment of alcoholism.”

http://www.ncbi.nlm.nih.gov/pubmed/15542757

Neuromodulatory role of the endocannabinoid signaling system in alcoholism: an overview.

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Abstract

“The current review evaluates the evidence that some of the pharmacological and behavioral effects of ethanol (EtOH), including EtOH-preferring behavior, may be mediated through the endocannabinoid signaling system. The recent advances in the understanding of the neurobiological basis of alcoholism suggest that the pharmacological and behavioral effects of EtOH are mediated through its action on neuronal signal transduction pathways and ligand-gated ion channels, receptor systems, and receptors that are coupled to G-proteins. The identification of a G-protein-coupled receptor, namely, the cannabinoid receptor (CB1 receptor) that was activated by Delta(9)-tetrahydrocannabinol (Delta(9)-THC), the major psychoactive component of marijuana, led to the discovery of endogenous cannabinoid agonists. To date, two fatty acid derivatives identified to be arachidonylethanolamide (AEA) and 2-arachidonylglycerol (2-AG) have been isolated from both nervous and peripheral tissues. Both these compounds have been shown to mimic the pharmacological and behavioral effects of Delta(9)-THC. The involvement of the endocannabinoid signaling system in the development of tolerance to the drugs of abuse including EtOH has not been known until recently. Recent studies from our laboratory have demonstrated for the first time the down-regulation of CB1 receptor function and its signal transduction by chronic EtOH. The observed down-regulation of CB1 receptor binding and its signal transduction results from the persistent stimulation of the receptors by the endogenous CB1 receptor agonists, AEA and 2-AG, the synthesis of which has been found to be increased by chronic EtOH treatment. This enhanced formation of endocannabinoids may subsequently influence the release of neurotransmitters. It was found that the DBA/2 mice, known to avoid EtOH intake, have significantly reduced brain-CB1-receptor function consistent with other studies, where the CB1 receptor antagonist SR141716A has been shown to block voluntary EtOH intake in rodents. Similarly, activation of the CB1 receptor system promoted alcohol craving, suggesting a role for the CB1 receptor gene in excessive EtOH drinking behavior and development of alcoholism. Ongoing investigations may lead to the development of potential therapeutic strategies for the treatment of alcoholism.”

http://www.ncbi.nlm.nih.gov/pubmed/12052043