Stress or drug priming induces reinstatement of extinguished conditioned place preference.

To construct a model for the relapse of drug use, we investigated the reinstatement of morphine-induced conditioned place preference (CPP) in rats. After the morphine CPP paradigm was established, rats were left extinguishing for 9 days, then exposed to 15 min of random foot shock or s.c. drug priming with different doses of morphine or amphetamine, respectively. Foot shock or a higher dose (0.25 mg/kg) of both drugs could reinstate the CPP induced by 4 mg/kg of morphine after a 9-day extinction, while a lower dose (0.125 mg/kg) of both drugs had no effect. It is concluded that the CPP extinction-reinstatement paradigm might be used as a model to investigate the mechanism of relapse in addicts.