Deficits of Morris water maze learning in rats with striatal kainic acid lesions.

This study investigated effects of intrastriatal kainic acid administration, which induces selective neuronal cell death in the striatum sparing passing nerve fibers and terminals, on the acquisition of spatial learning in Morris water maze. Rats treated with bilateral kainic acid (0.5-1.0 microgram) into the striatum were trained to escape to a hidden platform under the water. Compared with control rats, kainic acid (1.0 microgram)-lesioned rats showed significantly longer escape latency in the place navigation, and in the following probe test lower rate of swimming within the quadrant where the platform had been placed. In addition, kainic acid (1.0 microgram)-lesioned rats showed longer latency in the cue navigation in which rats were trained to escape to a visible platform above the water. These deficits were caused by their tendency to swim along the wall of pool before approaching the platform and not by their swim difficulty. Results suggest that striatal neurons or neural circuits containing these neurons play an important role in the acquisition of spatial learning task, and the nature of this performance impairment was discussed in terms of both learning and attention deficits.