EFFECTS OF NALOXONE ON LIMITED-ACCESS ETHANOL DRINKING IN RATS

The hypothesis that naloxone (NAL) decreases oral ethanol intake in ra ts by inducing a conditioned taste aversion (CTA) to ethanol was inves tigated. Rats were trained to drink 8% ethanol (v/v) on a 1-hr limited -access schedule. They received 4 days of intraperitoneal injections o f 10 mg/kg of NAL, 10 min before limited-access (-10MIN group), immedi ately after limited-access (1HR group), or 3 hr after limited-access ( 3HR). Ethanol intake decreased in the -10MIN and 1HR groups during the injection period and on the postinjection day. In experiment 2, rats received 4 days of NAL injections when ethanol was not available (pre- exposure), and then the paradigm was repeated. In this experiment, the re was no suppression of ethanol intake for any group on the postinjec tion day. The decrease in ethanol intake during injections observed fo r the 1HR in experiment 1 and the sustained suppression postinjection was interpreted as a CTA. Preexposure in experiment 2 abolished the CT A. Differences in the pattern ethanol intake for the -10MIN and 3HR gr oups during the experiments, however, suggest that a CTA is not the so le mechanism underlying NAL's suppressant effects on ethanol intake. I n conclusion, in rats both the dose of NAL and the relative timing of NAL injections and ethanol drinking effect subsequent NAL suppression of ethanol intake.