Figure 1.

β‐Endorphin (β‐E) masks sex differences in binge‐like EtOH drinking. (a) Daily consumption of 20% EtOH versus water across the 2‐hour sessions (days 1–3) and 4‐hour binge test (day 4) of the drinking in the dark procedure. A repeated measures ANOVA across days 1–3 revealed a significant sex by genotype interaction, and post hoc analysis indicated that β‐E −/− female mice consumed more EtOH than β‐E −/− male mice. A two‐way ANOVA on the day 4 binge test (BT) revealed a main effect of sex (female mice > male mice) and a sex by genotype interaction. There was a main effect of sex and a sex by genotype interaction for the 4‐hour BT. Post hoc analysis indicated that β‐E −/− female mice consumed more EtOH than β‐E −/− male mice. (b) These data are summarized as average consumption across the 4‐day paradigm. There was a main effect of sex (female mice > male mice), and a sex by genotype interaction with post hoc analysis indicating that β‐E −/− female mice consumed more EtOH overall than β‐E +/− and β‐E +/+ female and β‐E −/− male mice. Data are presented as means ± SEM; *P < 0.05 (Bonferroni corrected); n for each group are displayed within their respective bar