Naloxone-precipitated morphine withdrawal induced place aversions: effect of naloxone at 24 hours postmorphine.

The aversive properties of naloxone-precipitated withdrawal from acutely administered morphine were assessed using the place-conditioning paradigm. The conditioned place aversion produced by naloxone (0.5-1.0 mg/kg, s.c.) after two conditioning trials was enhanced by pretreatment with morphine (20 mg/kg, s.c.) 24 h prior to the conditioning trial. Naloxone precipitated withdrawal from acutely administered morphine produces an aversive motivational state that becomes associated with place cues.