Interaction of cannabinoid receptor 2 and social environment modulates chronic alcohol consumption.

Genetic and environmental factors contribute nearly with equal power to the development of alcoholism. Environmental factors, like negative life events or emotionally disruptive conditions initiate and promote alcohol drinking and relapse. The endocannabinoid system is involved in hedonic control and modulates stress reactivity. Furthermore, chronic alcohol drinking alters endocannabinoid signalling, which in turn influences the stress reactivity. Recently it has been shown that CB2 receptor activity influences stress sensitivity and alcohol drinking. We hypothesised that CB2 receptors influence the impact of environmental risk factors on alcohol preference and consumption. Therefore, in this study we investigated the alcohol-drinking pattern of wild type and CB2 deficient animals under single and group housing conditions using different alcohol drinking models, like forced drinking, intermittent forced drinking and two-bottle choice paradigms. Our data showed that CB2 receptor modulates alcohol consumption and reward. Interestingly, we detected that lack of CB2 receptors led to increased alcohol drinking in the intermittent forced drinking paradigm under group housing conditions. Furthermore, we found that CB2 knockout mice consumed more food and that their body weight gain was modulated by social environment. On the base of these data, we conclude that social environment critically affects the modulatory function of CB2 receptors especially in alcohol intake. These findings suggest that a treatment strategy targeting CB2 receptors may have a beneficial effect on pathologic drinking particularly in situations of social stress and discomfort.
Copyright © 2015. Published by Elsevier B.V.