Circadian clock genes Bmal1 and Per2 in the nucleus accumbens are negative regulators of alcohol-drinking behavior in mice.

Voluntary alcohol consumption is influenced by a variety of environmental and genetic factors, including circadian clock genes. Even though their sex-specific role in alcohol drinking was identified through selective ablation of Bmal1 and Per2 from neurons of the mouse striatum, the contribution of specific striatal subregions to the observed drinking behavior remains unclear. Thus, alcohol intake and preference was investigated in male and female mice with a conditional knockout of Bmal1 and Per2 from cells in the nucleus accumbens (Nac). Mood- and anxiety-related behaviors were assessed prior to alcohol drinking to exclude potential confounding effects of the animals behavioral state on alcohol consumption. Alcohol consumption and preference were increased in male and female mice with a conditional knockout of Bmal1, whereas the same effect was only found in males with a deletion of Per2. Because affective behaviors were only mildly influenced by the conditional gene knockouts, observed alcohol-drinking phenotypes can be directly associated with the Nac-specific clock gene deletion. The results thus suggest an inhibitory role of Bmal1 and Per2 in the Nac on alcohol consumption in male mice. In females, the inhibitory effect of Bmal1 is strictly localized to the Nac, because striatal-wide deletion of Bmal1 caused a suppression of alcohol consumption. This sex-dependent stimulatory effect of Bmal1 on alcohol drinking is probably mediated through other striatal subregions such as the dorsal striatum.