RESUMO
After introcerebroventricular injection of kainic acid(KA) in the awake rat, three types of hippocampal unit responses, i. e- positive units, negative units and indifferent units, were recorded- Most positive units were hippocampal complex spike cells which correspond histologically to hippocampal pyramidal cells, and most hippocampal complex spike cells fired in positive bursts after KA treatment. In the early period after KA injection, the positive units were concentrated in CA3 area. It was suggested that:(1)the activities of positive units may be considered as the typical epileptiform hippocampal unit activity induced by KA, and the firing characteristics of the negative units may be the result of influence of hippocampal inhibitory interneurons or that of the excessive cellular depolarization;(2) the hippocampal pyramidal cells were more sensitive to the epileptogenic effect of KA than the hippocampal interneurons, and some pyramidal cells in CA3 area may serve as "pacemaker neurons" in KA induced epileptogenesis.