[Effects of excluding reticuloseptal input on hippocampal electrical activity in the cat]

The effect of interruption of the reticulo-septal input on the electrical activity of CA1 and CA3 areas of the dorsal hippocampus was studied in cats. Lesion of the medial septal nuclei or the i.v. injection of chlorpromazine in low doses led to depression of the hippocampal theta activity. The reticulo-septal input is responsible for generation and the course of tonic sensory responses of the hippocampal neurons in both areas. The existence of the remaining principal types of sensory responses (phasic, complex) mainly depends upon the cortical input. The reticulo-septal input takes part only in the prolongation of these responses.