Context-specific morphine withdrawal in rats: duration and effects of clonidine.

Rats previously injected with morphine in a particular environment (paired rats) emitted more withdrawal symptoms in that environment than did rats previously injected with morphine in another environment (unpaired rats) after both 1 day and 5 days of morphine abstinence. Thus, reexposure to an environment previously associated with morphine can elicit context-specific withdrawal even after several days of morphine abstinence. Clonidine (0.06 mg/kg) reduced most of the withdrawal symptoms seen 5 days after morphine abstinence in both the paired and unpaired rats. However, clonidine enhanced many of the withdrawal symptoms in both groups of rats during naltrexone-precipitated withdrawal 1 day after morphine abstinence.