Gonadal Sex and Sex-Chromosome Complement Interact to Affect Ethanol Consumption in Adolescent Four Core Genotypes Mice

ABSTRACT Background Sex differences in ethanol consumption have been reported in both humans and laboratory rodents, but the independent/dependent contributions of genetic and hormonal sex◻biasing mechanisms to these phenotypes have not yet been fully explored. Methods To examine the contributions of sex-chromosome complement (SCC) and gonadal sex (GS) to ethanol consumption, we studied adolescent (28-32 days old) four core genotypes (FCG) mice (C57BL/6J background; FCG model allows for independent assortment of GS and SCC) using a modified drinking-in-the-dark (DID) procedure. Mice were offered concurrent access to 20%, 10% and 0% ethanol (in water) in four daily 2-hour sessions. Consumption at the level of individual bouts was recorded. Results Although all four genotype groups preferred the 20% ethanol over 10% and 0%, and showed similar consumption of the 10% and 0% solutions, the group rankings for consumption of the 20% ethanol solution were XX+testes > XY+testes > XY+ovaries > XX+ovaries. Thus, an interaction was observed between SCC and GS for which the simple effect of SCC was greatest in mice with ovaries (XY > XX) and the simple effect of GS was greatest in XX mice (testes > ovaries). Moreover, these effects varied in magnitude across and within drinking sessions. The behavioral microstructure of ethanol consumption (i.e., parameterization of within-session discriminable drinking bouts) support the validity of our 3-bottle modification of the DID procedure as a model of binge-like consumption as: (1) the consumption rate of the 20% ethanol solution was ~80 g EtOH/kg/h within a bout (~12 s/bout, ~3 bouts/session), (2) most of this ethanol consumption was completed in a single bout and (3) within-session ethanol consumption was greater earlier than later, indicating “front loading.” Conclusions These results indicate that SCC and GS interact on ethanol consumption in adolescent FCG mice on a C57BL/6J background to affect binge-like consumption from the very initiation of access and that these effects are dynamic as they varied both across and within sessions. Highlights Gonadal sex and sex-chromosome complement interact on ethanol consumption in adolescent four core genotypes mice In adolescent four core genotypes mice, mice with testes drink more ethanol than mice with ovaries, particularly in the presence of an XX karyotype In adolescent four core genotypes mice, XY mice drink more ethanol than XX mice, but only in mice with ovaries The effects of sex-biasing biological factors on the patterns of ethanol consumption by adolescent four core genotypes mice that we observed in our 3-bottle Drinking-in-the-Dark procedure showed face validity with some of the sex/gender differences observed in human adolescents