Spatial localization in the Morris water maze in rats: acquisition is affected by intra-accumbens injections of the dopaminergic antagonist haloperidol.

Previous studies (G. E. Ploeger, B. M. Spruijt, & A. R. Cools, 1992) showed that low doses of systemically injected haloperidol affected spatial learning in the Morris water maze. This study investigated effects of intra-accumbens injections of haloperidol on spatial learning. To control for motivation and sensorimotor coordination, the researchers trained the rats to escape onto a visible platform. Low doses (50-100 ng) of haloperidol impaired spatial learning, whereas escaping on a visible platform was undisturbed. The 500-ng dose of haloperidol completely blocked acquisition because of combined learning and motor impairments. Retrieval of an acquired escape response was unaffected by 500 ng haloperidol. The data show that mesolimbic dopaminergic activity is involved in the acquisition of spatial localization. The results are related to studies demonstrating the involvement of the nucleus accumbens in cue-directed behaviors.