The locomotor and exploratory activities in rats after lesion of hippocampal pyramidal cells with kainic acid.

The effect of single kainic acid (KA) intracerebroventricular(icv) injection on spontaneous locomotor, exploratory, basal and total activities in rats measured a different times was tested. Whereas at 3 hr after KA icv administration an increase of the total, basal and spontaneous activities of rats were observed, a great decrease of the exploratory activity was noted. KA at 24 hr after its administration depressed all types of rats activities. From 72nd hr after KA icv injection a significant increase in the total, exploratory and spontaneous locomotor activities without changes in the basal activity was observed. The above mentioned changes persisted up to 10-20 days after KA administration. The histological examinations showed evident neuropathologic changes in hippocampal stratum pyramidale. The most evident changes concerned the hippocampal areas CA3/CA4 and CA1. There were observed shrinking, narrowing and fragmentation of pyramidal cells. An intense progressive gliotic reaction was present among the fragmented cells, the layer of pyramidal cells being considerably diminished.