Involvement of CB2 cannabinoid receptor in the reinforcing effects of chocolate flavoured-pellets and eating addictive-like behaviour.

This study was aimed to evaluate the involvement of CB2 cannabinoid receptor (CB2R) in the reinforcing effects and eating addictive-like behaviour promoted by chocolate-flavoured pellets. We used a recently validated operant model of eating addictive-like behaviour in mice deficient or overexpressing CB2R and wild-type littermates (WT). Three hallmarks of addiction were evaluated at two different time points during the early and late training period in this model: persistence of food seeking during a period of nonavailability of food, motivation for food and perseverance of responding when the reward was associated with a punishment. Each mouse was classified as resistant (0 criteria) or vulnerable (2-3 criteria) to this addictive-like behaviour considering these hallmark criteria. Our results revealed a significant difference in the percentage of mice reaching 0 criteria when compared CB2R deficient mice (0%) with control mice (60%) during the early period, although no major differences were reported between mice overexpressing the CB2 protein (33.3%) and control mice. During the late period, a reduced but not significant percentage of CB2R knockout mice resistant to addiction was shown, suggesting that CB2R seems involved in the predisposition to addiction. Thus, CB2R may constitute an interesting potential mechanism involved in eating addictive-like behaviours.