The contributions of taste cues to ethanol responses in female and male rats

Bitter-tasting stimuli, like ethanol (EtOH), are innately avoided yet variability in orosensory-driven behaviors may contribute to differences in ethanol intake. Experiment 1 was designed to test the hypothesis that there are sex differences in the taste qualities of ethanol. Female and male rats were presented 5 or 10 % EtOH followed by administration (i.p.) of LiCl to induce visceral malaise, or saline as a control. Generalization of the conditioned avoidance was assessed in a brief-access taste test (10-s trials; 30-min session) in which water, 0.03 and 0.3 M sucrose ("sweet"), 0.03 and 0.3 mM quinine ("bitter") and sucrose-quinine mixtures were presented in randomized blocks without replacement. Conditioned avoidance of ethanol generalized to sucrose and sucrose-quinine mixtures. In experiment 2, unconditioned lick responses to an array of ethanol concentrations (1-32 %) were measured in rats following administration (i.p.) of saline, 0.1 or 1.0 mg/kg naltrexone, an opioid receptor antagonist. Compared to saline, naltrexone administration lowered trials initiated for both sexes, but decreased responses to 32 % ethanol only for males. Together these findings indicate the oral qualitative profile of ethanol is comparable and the sucrose-like component is most salient in both sexes. Opioidergic signaling that drives the appetitive components of behavior towards ethanol is similar for females and males but differs for some components of consummatory behavior. Thus, sex differences in responses to ethanol do not appear to be primarily driven by variability in qualitative components of ethanol that contributes to consummatory aspects of ingestive behavior, but more likely by reward-related signaling.