The clock gene Bmal1 plays an obligatory role in the generation of circadian rhythms in gene expression, physiology, and behavior in mammals. In mice, perturbations in Bmal1 expression in the brain are associated with loss of circadian rhythmicity and various physiological and behavioral disturbances, including disrupted sleep architecture and deficits in cognitive and affective behaviors. Gene association studies in both humans and animals suggest that Bmal1 may also play a role in the control of appetitive behaviors such as alcohol preference and consumption. Although there is evidence that genes that interact with Bmal1 in the molecular circadian clock, such as Per2 and Clock influence alcohol intake and preference, experimental evidence of a causal role of Bmal1 is lacking. In addition, the specific brain regions where Bmal1 might affect alcohol consumption are not known. We investigated voluntary alcohol consumption in conditional knockout mice that lack BMAL1 protein exclusively in the striatum, which is an important structure in the control of alcohol intake and preference. Particular emphasis was attributed to the investigation of male and female mice because of known sex differences in alcohol intake and preference, and the impact of a sexually dimorphic constitution of circadian clocks on behavior. We found that deletion of BMAL1 from the principal medium spiny neurons (MSNs) of the striatum significantly altered voluntary alcohol intake and preference, without affecting total fluid intake, sucrose preference, body weight, or circadian rhythms in behavior. Strikingly, there were major sex differences in the effect of striatal BMAL1 deletion on alcohol consumption. While striatal BMAL1 deletion augmented alcohol intake and preference in males, the same deletion suppressed intake and preference in females. Interestingly, striatal deletion of PER2, a clock gene that interacts with Bmal1 in the circadian clock, and which has been shown to limit alcohol consumption in mice, mimicked the effect of striatal BMAL1 deletion, albeit only in males. Together, our results reveal that BMAL1 in MSNs of the striatum plays a sexually dimorphic role in the control of alcohol intake in mice, restraining consumption in males, possibly by interacting with PER2, and promoting intake in females, independently of PER2. We therefore hypothesize that a sex-specific mechanism in the function of BMAL1 in MSNs of the striatum regulates differences between male and female mice in the propensity to consume alcohol.
bioRxiv Subject Collection: Neuroscience