Mice expressing a "hyper-sensitive" form of the $\mathrm{CB_1}$ cannabinoid receptor ( $\mathrm{CB_1}$) show modestly enhanced alcohol preference and consumption

We recently characterized S426A/S430A mutant mice expressing a desensitization-resistant form of the $\mathrm{CB_1}$ receptor. These mice display an enhanced response to endocannabinoids and $\mathrm{∆^9}$-THC. In this study, S426A/S430A mutants were used as a novel model to test whether ethanol consumption, morphine dependence, and reward for these drugs are potentiated in mice with a “hyper-sensitive” form of $\mathrm{CB_1}$. Using an unlimited-access, two-bottle choice, voluntary drinking paradigm, S426A/S430A mutants exhibit modestly increased intake and preference for low (6%) but not higher concentrations of ethanol. S426A/S430A mutants and wild-type mice show similar taste preference for sucrose and quinine, exhibit normal sensitivity to the hypothermic and ataxic effects of ethanol, and have normal blood ethanol concentrations following administration of ethanol. S426A/S430A mutants develop robust conditioned place preference for ethanol (2 g/kg), morphine (10 mg/kg), and cocaine (10 mg/kg), demonstrating that drug reward is not changed in S426A/S430A mutants. Precipitated morphine withdrawal is also unchanged in opioid-dependent S426A/S430A mutant mice. Although ethanol consumption is modestly changed by enhanced $\mathrm{CB_1}$ signaling, reward, tolerance, and acute sensitivity to ethanol and morphine are normal in this model