THE NMDA RECEPTOR AND COCAINE - EVIDENCE THAT MK-801 CAN INDUCE BEHAVIORAL SENSITIZATION EFFECTS

Antagonism of the NMDA receptor with MK-801 is considered to be an eff ective pharmacologic manipulation to prevent the development of sensit ization effects to drugs such as cocaine. The present study investigat ed this issue by comparing the behavioral response of separate groups of rats to three treatment cycles of either saline, 0.1 mg/kg MK-801, 10 mg/kg cocaine, or combined MK-801-cocaine (0.1/10 mg/kg). The treat ments were spaced 1 week apart and were preceded by two nondrug baseli ne tests. In the first test cycle, the four groups had equivalent acti vity levels in the two nondrug tests. In the first drug test only the MK-801-cocaine group exhibited hyperactivity. By the third drug test, the MK-801-cocaine group exhibited an enhanced hyperactivity and the M K-801 group became hyperactive. Thus, behavioral drug sensitization de veloped but only with groups treated with MK-801. Antagonism of the NM DA receptor under some circumstances can be a highly effective treatme nt for the induction of behavioral sensitization effects.