Decrease in ethanol consumption by naloxone in naive and dependent rats.

Acute effects of the opiate antagonist, naloxone, on alcohol intake have been examined and compared in naive and behaviorally dependent rats. In naive rats the aversion to an 8% alcohol solution exhibited in a 30 min presentation was selectively augmented by an IP administration of naloxone (1 mg/kg) 30 min before a morning drinking session. In other rats, behavioral dependence was established by 15 days of IG administration of intoxicating doses of alcohol. This dependence was exhibited by a sustained preference for ethanol for 6 days. Naloxone (1 mg/kg) abolishes the acquired preference for ethanol tested during an 8 hour day time presentation. These effects of naloxone on alcohol intake in ethanol naive and dependent rats are interpreted in relation to a general non-specific action of naloxone on preferred or aversive flavoured solutions.