Effect of electrical stimulation of the septum on subicular neurons with different kinds of spontaneous activity in rabbits

Abstract

The effect of electrical stimulation of the medial nucleus of the septum and of hippocampal area CA1 on subicular neurons with three different types of spontaneous activity (with theta-modulation, with delta-modulation and complex spikes, and with irregular single-spike activity) was studied in unanesthetized rabbits by extracellular recording of unit activity. Cells with theta-activity were found to respond in a distinctive functional manner to stimulation of the medial nucleus of the septum: Their reactivity was higher but latent periods of their responses were much shorter than those of cells with delta-activity and irregular discharges. Stability of modulation of theta-cell activity increased both during and after stimulation of the medial septal nucleus. Electrical stimulation of hippocampal area CA1, on the other hand, led to disappearance of rhythm modulation. Average response latencies of all three types of cells to stimulation of area CA1 were equal. The results indicate special properties of the septal input to subicular cells with theta-modulation.