COCAINE- AND AMPHETAMINE-REGULATED TRANSCRIPT (CART) MEDIATES SEX DIFFERENCES IN BINGE DRINKING THROUGH CENTRAL TASTE CIRCUITS

Binge drinking is a dangerous form of alcohol consumption that strongly predicts the future development of alcohol use disorder. However, despite its prevalence, the neural mechanisms involved, and potential sex differences, remain mostly unknown. The neuropeptide cocaine- and amphetamine-regulated transcript (CART) has previously been implicated in reward, feeding and stress-related behaviours, but has not yet been investigated in the context of binge drinking.

Thus, we examined sex differences in the role of CART in binge drinking.

Male and female CART KO and WT mice underwent three 2-hour binge drinking sessions/week, where the water bottle was replaced with a bottle containing 10% v/v ethanol. Once stable drinking levels were achieved, mice completed a 4-hour test session. We next examined the potential role of peripherally circulating sex steroid hormones on binge drinking. Female CART KO mice underwent ovariectomy or SHAM surgery during binge drinking training. After surgery, recovery and re-training mice were tested in a 4-hour test session. We then assessed the effect of global CART KO on continuous alcohol intake and taste preference in two separate cohorts. Male and female CART KO and WT mice had continuous access to a bottle containing water and a bottle containing either increasing concentrations of ethanol (5/20% v/v) or a bottle containing a tastant (sweet, salty, sour and bitter). Finally, to assess the involvement of CART signalling in a key node of the taste circuit, we implanted cannulas into the central amygdala (CeA) during binge drinking training. Following recovery, re-training and habituation, mice were infused with either CART antibody or vehicle into the CeA immediately prior to testing, and were tested with the opposite treatment condition following re-training. Here, male and female mice were presented with either 10% v/v ethanol or 10% v/v ethanol supplemented with 5% w/v sucrose.

Firstly, we observed a sexual dimorphism in binge drinking; male CART KO mice increased, whilst female CART KO mice decreased, alcohol intake compared to WT littermates. In female CART KO mice, ovariectomy had no effect on alcohol intake compared to SHAM surgery mice, discounting the involvement of circulating sex steroid hormones. Interestingly, assessment of taste perception revealed female CART KO mice to also have reduced intake of quinine, a bitter solution with a similar taste profile to alcohol. Enhancing the palatability of both alcohol and quinine via sucrose supplementation returned consumption and preference in female CART KO mice to WT levels, implicating the potential involvement of central taste circuits. Indeed, neutralisation of CART signalling in the CeA reduced plain alcohol, but not sweetened alcohol, binge drinking in female mice, whilst eliciting no change in male mice.

Collectively, these data show a novel sexually dimorphic role for CART in binge drinking, which may be driven via changes in bitter taste sensitivity. Further, CeA CART signalling is critically involved in binge drinking specifically in female mice. Therefore, future research targeting the CART system may reveal novel insights for alcohol use disorder that may have heightened efficacy in females.