Generally, antipsychotic agents are dopamine receptor blocking agents that also block conditioned avoidance responding (CAR) in the rat. Recently, however, both (0- methoxypheny1) piperazine (OMPP, lh) and (m-chloropheny1) piperazine (MCPP, lo) have been reported to block conditioned avoidance responding in the rat although neither has dopamine receptor blocking properties. The present paper examines the behavioral and ...