SPATIAL LOCALIZATION IN THE MORRIS WATER MAZE IN RATS - ACQUISITION IS AFFECTED BY INTRAACCUMBENS INJECTIONS OF THE DOPAMINERGIC ANTAGONISTHALOPERIDOL

Previous studies (G. E. Ploeger, B. M. Spruijt, and A. R. Cools, 1992) showed that low doses of systemically injected haloperidol affected s patial learning in the Morris water maze. This study investigated effe cts of intra-accumbens injections of haloperidol on spatial learning. To control for motivation and sensorimotor coordination, the researche rs trained the rats to escape onto a visible platform. Low doses (50-1 00 ng) of haloperidol impaired spatial learning, whereas escaping on a visible platform was undisturbed. The 500-ng dose of haloperidol comp letely blocked acquisition because of combined learning and motor impa irments. Retrieval of an acquired escape response was unaffected by 50 0 ng haloperidol. The data show that mesolimbic dopaminergic activity is involved in the acquisition of spatial localization. The results ar e related to studies demonstrating the involvement of the nucleus accu mbens in cue-directed behaviors.