Caffeine promotes an ethanol-induced conditioned taste aversion: a dose-dependent interaction

The present study examined whether caffeine administered within a dose range previously shown to promote ethanol drinking would also alter an ethanol-induced conditioned taste aversion (CTA). The results revealed a dose-dependent interaction between caffeine and ethanol where caffeine (2.5 and 10 mg/kg) promoted an ethanol-induced CTA at a low ethanol dose (1.0 g/kg) but had no effect in blocking CTA at the higher ethanol dose (1.5 g/kg). These results were found to be unrelated to an alteration in ethanol metabolism, as caffeine had no effect in altering blood ethanol levels at the doses tested. In agreement with the reward comparison hypothesis, the present results suggest that rather than attenuate ethanol's "aversive" effects, caffeine may have promoted an ethanol-induced CTA by increasing the reinforcing efficacy of ethanol.