THE DEVELOPMENT OF BEHAVIORAL SENSITIZATION TO APOMORPHINE IS BLOCKEDBY MK-801

The effects of the non-competitive NMDA receptor antagonist, MK-801 (d izocilpine), on the development of sensitization to the mixed dopamine receptor agonist, apomorphine were examined. Rats pretreated with MK- 801 (0.25 mg/kg) prior to 2.0 mg/kg apomorphine failed to show a progr essive sensitization to the activating effect of apomorphine across si x preexposure sessions, nor did they show enhanced activity relative t o control rats in response to 0.5 mg/kg apomorphine, given alone, duri ng a subsequent test for sensitization. These results support the view that MK-801 interferes with long-term neural changes underlying sensi tization to stimulant drugs.