Monthly Archives: October 2012

CB1 receptor antagonists for the treatment of nicotine addiction.

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Abstract

“Tobacco smoking is the largest cause of avoidable death and disease in developed countries. It is now viewed as a complex bio-psycho-social problem for which effective pharmacological treatments are needed. Nicotine is considered to be the primary compound of tobacco smoke that establishes and maintains tobacco dependence. The addictive effect of nicotine is mediated by activation of the mesolimbic system and the release of dopamine in the nucleus accumbens. Recently, the existence of a specific functional interaction between nicotine and the endocannabinoid system has been reported. Co-administration of sub-threshold doses of a cannabinoid agonist and nicotine produces rewarding effects and chronic nicotine treatment increases endocannabinoid levels in limbic regions. The CB1 receptor plays a key role in this interaction. CB1 knockout mice are less sensitive to the motivational effects of nicotine although this depends on the experimental model. The selective CB1 antagonist, rimonabant (SR141716), reduces nicotine self-administration and nicotine-seeking behavior induced by conditioned cues in rats. Rimonabant appears to reduce nicotine addiction by attenuating the hyperactivation of the endocannabinoid system and the mesolimbic dopaminergic neuronal pathway. Rimonabant may be considered as a potential alternative to the current substitutive treatments of nicotine addiction and may offer a new hope for the treatment of smokers who wish to quit.”

http://www.ncbi.nlm.nih.gov/pubmed/15935455

Cannabinoid type 1 receptor antagonists (rimonabant) for smoking cessation.

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“BACKGROUND:

Rimonabant is a selective type 1 cannabinoid (CB1) receptor antagonist. It may assist with smoking cessation by restoring the balance of the endocannabinoid system, which can be disrupted by prolonged use of nicotine. Rimonabant also seeks to address many smokers’ reluctance to persist with a quit attempt because of concerns about weight gain.”

“OBJECTIVES:

To determine whether selective CB1 receptor antagonists increase the numbers of people stopping smoking. To assess their effects on weight change in successful quitters and in those who try to quit but fail.”

“AUTHORS’ CONCLUSIONS:

From the preliminary trial reports available, rimonabant 20 mg may increase the odds of quitting approximately 1(1/2)-fold. Adverse events include nausea and upper respiratory tract infections; the risk of serious adverse events is reported to be low. However, there is current concern (August 2007) over rates of depression and suicidal thoughts in people taking rimonabant for weight control. The evidence for rimonabant in maintaining abstinence is inconclusive. Rimonabant 20 mg may moderate weight gain in the long term.”

http://www.ncbi.nlm.nih.gov/pubmed/17943852

Cannabinoid type 1 receptor antagonists for smoking cessation.

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Abstract

“BACKGROUND:

Selective type 1 cannabinoid (CB1) receptor antagonists may assist with smoking cessation by restoring the balance of the endocannabinoid system, which can be disrupted by prolonged use of nicotine. They also seeks to address many smokers’ reluctance to persist with a quit attempt because of concerns about weight gain.”

“OBJECTIVES:

To determine whether selective CB1 receptor antagonists (currently rimonabant and taranabant) increase the numbers of people stopping smoking To assess their effects on weight change in successful quitters and in those who try to quit but fail.”

“AUTHORS’ CONCLUSIONS:

From the trial reports available, rimonabant 20 mg may increase the chances of quitting approximately 1½-fold. The evidence for rimonabant in maintaining abstinence is inconclusive. Rimonabant 20 mg may moderate weight gain in the long term. Taranabant 2-8 mg may moderate weight gain, at least in the short term. In 2008, development of both rimonabant and taranabant was discontinued by the manufacturers.”

http://www.ncbi.nlm.nih.gov/pubmed/21412887

The endocannabinoid system: a new molecular target for the treatment of tobacco addiction.

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Abstract

“Tobacco addiction is one of the leading preventable causes of mortality in the world and nicotine appears to be the main critical psychoactive component in establishing and maintaining tobacco dependence. Several lines of evidence suggest that the rewarding effects of nicotine, which underlie its abuse potential, can be modulated by manipulating the endocannabinoid system. For example, pharmacological blockade or genetic deletion of cannabinoid CB(1) receptors reduces or eliminates many behavioral and neurochemical effects of nicotine that are related to its addictive potential. This review will focus on the recently published literature about the role of the endocannabinoid system in nicotine addiction and on the endocannabinoid system as a novel molecular target for the discovery of medications for tobacco dependence.”

http://www.ncbi.nlm.nih.gov/pubmed/19128204

Addiction and the pharmacology of cannabis: implications for medicine and the law.

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Abstract

“The topic of drug addiction or misuse of drugs has numerous far-reaching ramifications into areas such as neuroscience, medicine and therapeutics, toxicology, epidemiology, national and international economics and politics, and the law. The general principles of drug addiction are first summarised. A recurring and intrinsic problem is lack of adequate characterisation of the independent variable, namely the drug taken. Secondly, it is not feasible to allocate subjects randomly to treatments. Thirdly, the heterogeneity of different forms of addiction precludes facile generalisations. “A problem drug user is anyone who experiences social, psychological, physical, or legal problems related to intoxication, and/or regular excessive consumption, and/or dependence as a consequence of their use of drugs” (UK Advisory Council on Misuse of Drugs, 1982). Cannabis is a genus of flowering plants whose products are used as recreational drugs. Claims have been made for a range of therapeutic properties. Its two main active principles are delta9 – tetrahydrocannabinol (THC) and cannabidiol (CBD). These compounds have contrasting pharmacological properties. THC is suspected of causing psychotic phenomena, but CBD seems more sedative and may even be antipsychotic. The past use of cannabis, particularly the concentrations of THC and CBD, can be monitored with hair analysis. Recent studies involving the administration of THC and CBD to human subjects are reviewed. Suggestions are made for further research into the pharmacology and toxicology of CBD. Such data may also point to a more rational evidence-based approach to the legal control of cannabis preparations.”

http://www.ncbi.nlm.nih.gov/pubmed/19306615

Involvement of cannabinoid CB1 receptors in drug addiction: effects of rimonabant on behavioral responses induced by cocaine.

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Abstract

“A lot of evidence indicate that endocannabinoids and cannabinoid CB(1) receptors are implicated in drug addiction. In the present study, we investigated the effect of the cannabinoid CB(1) receptor antagonist/partial agonist rimonabant on the cocaine-maintained reinforcement and relapse to cocaine seeking as well as on the cocaine challenge-induced hyperactivity in sensitized rats and on discriminative stimulus effects of cocaine in rats. We found that endocannabinoids were not involved in maintenance of cocaine reinforcement and its subjective effects since pharmacological blockade of cannabinoid CB(1) receptors altered neither self-administration nor discriminative stimulus effects of cocaine. On the other hand, withdrawal from repeated access or exposure to cocaine and then a reinstatement of cocaine-seeking behavior or a sensitized locomotor response to a single cocaine challenge, respectively, was potently reduced by pretreatment with rimonabant. The latter observations may show that repeated cocaine treatment and the drug withdrawal produce–apart from behavioral effects–also different neural consequences in the endocannabinoid systems in rats.”

http://www.ncbi.nlm.nih.gov/pubmed/17220538

A Role for the Endocannabinoid System in the Increased Motivation for Cocaine in Extended Access Conditions

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 “Extended access to cocaine produces an increase in cocaine self-administration in rats that mimics aspects of compulsive drug intake in human addicts. While emerging evidence implicates the endogenous cannabinoid system in aspects of opioid and ethanol addiction, a role of the endocannabinoid system in cocaine addiction remains largely inconclusive. Here, we investigate the effects of systemic and intra-accumbal administration of the CB1 antagonist SR141716A (Rimonabant) on cocaine self-administration (0.5 mg/kg/infusion) under a progressive ratio (PR) schedule in rats with extended (long access, LgA; 6 h/day) or limited (short access, ShA; 1 h/day) access to cocaine. LgA rats, but not ShA rats showed an increase in cocaine intake as previously reported, and responding for cocaine by LgA rats was higher than in ShA rats under a PR schedule. Systemic SR141716A induced a dramatic dose-dependent decrease in the break-point for cocaine by LgA rats, whereas only the highest dose of the antagonist had a significant effect in the ShA group. Anandamide levels in the nucleus accumbens (NAc) shell were decreased in ShA rats but unchanged in LgA rats during cocaine self-administration. Both phosphorylated and total CB1 receptor protein expression were upregulated in LgA rats in the NAc and the amygdala compared to ShA and drug-naïve rats, 24 h after last cocaine session. Finally, intra-NAc infusions of SR141716A reduced cocaine break-points selectively in LgA animals. These results suggest that neuroadaptations in the endogenous cannabinoid system may be part of the neuroplasticity associated with the development of cocaine addiction.”

“Taken together, our results suggest that eCB system neuroplasticity in the NAc may contribute to the motivational drive for cocaine associated with uncontrolled psychostimulant use and, therefore, may be a target for cocaine addiction pharmacotherapies.”

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2688678/

Antagonism of cannabinoid 1 receptors reverses the anxiety-like behavior induced by central injections of corticotropin-releasing factor and cocaine withdrawal.

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Abstract

“The endocannabinoid (eCB) system is an important regulator of the stress response and mediates several stress-related behaviors, including anxiety. Despite anatomical evidence that eCBs interact with the principle stress peptide, corticotropin-releasing factor (CRF), few data exist that address functional interactions between these systems. Accordingly, we examined the effects of the CB1 receptor antagonist, AM251, on behavioral anxiety induced by (1) exogenous CRF, and (2) withdrawal from chronic cocaine exposure (mediated by CRF). After behavioral testing, we collected blood and assessed plasma corticosterone levels. In Experiment 1, male Long-Evans rats were pretreated with AM251 (0, 10, 100, or 200 μg, i.c.v.), followed by CRF (0 or 0.5 μg, i.c.v.), before testing for anxiety-like behavior in the elevated plus maze (EPM). In Experiment 2, rats were exposed to cocaine (20 mg/kg, i.p.) or saline for 14 consecutive days. Forty-eight hours following cocaine exposure, rats were pretreated with AM251 (0, 10, or 100 μg, i.c.v.) and tested in the EPM. AM251 produced an anxiogenic response at the highest dose, but reversed the behavioral anxiety induced by CRF and withdrawal from chronic cocaine in a dose-dependent manner. AM251 also increased plasma corticosterone levels, but did so irrespective of CRF treatment or cocaine preexposure. Our findings suggest that the anxiogenic effects of CRF and cocaine withdrawal are mediated, at least in part, by CB1 receptor transmission, and provide evidence in support of eCB-CRF interactions that are independent of the hypothalamic-pituitary-adrenal axis.”

http://www.ncbi.nlm.nih.gov/pubmed/21784132

A cannabinoid mechanism in relapse to cocaine seeking.

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Abstract

“Treatment of cocaine addiction is hampered by high rates of relapse even after prolonged drug abstinence. This relapse to compulsive cocaine use can be triggered by re-exposure to cocaine, by re-exposure to stimuli previously associated with cocaine or by exposure to stress. In laboratory rats, similar events reinstate cocaine seeking after prolonged withdrawal periods, thus providing a model to study neuronal mechanisms underlying the relapse to cocaine. The endocannabinoid system has been implicated in a number of neuropsychiatric conditions, including drug addiction. The active ingredient of marijuana, Delta9-tetrahydrocannabinol, activates the mesolimbic dopamine (DA) reward system and has rewarding effects in preclinical models of drug abuse. We report here that the synthetic cannabinoid agonist, HU210 (ref. 13), provokes relapse to cocaine seeking after prolonged withdrawal periods. Furthermore, the selective CB1 receptor antagonist, SR141716A (ref. 14), attenuates relapse induced by re-exposure to cocaine-associated cues or cocaine itself, but not relapse induced by exposure to stress. These data reveal an important role of the cannabinoid system in the neuronal processes underlying relapse to cocaine seeking, and provide a rationale for the use of cannabinoid receptor antagonists for the prevention of relapse to cocaine use.”

http://www.ncbi.nlm.nih.gov/pubmed/11590440