EFFECTS OF CRH AND LHRH ON RAT SEPTOHIPPOCAMPAL NEURONS

Electrical activities of septum-diagonal band neurons (SD neurons) ant idromically activated by electrical stimulation of the fimbria were re corded in urethane anesthetized male rats. The mean basal firing rate of antidromically identified SD neurons (2.3 Hz) was not different fro m that of unidentified ones (2.2 Hz). The mean latency of antidromic a ctivation by the fimbria stimulation was 4.2 ms. Iontophoretically app lied CRH and LHRH affected 60% and 40% of identified SD neurons, but o nly 19% and 13% of unidentified SD neurons, respectively. The ratio of response to no response to both peptides was significantly different in unidentified SD neurons from that in identified SD neurons. These r esults suggest that SD neurons mediate the effect of CRH and LHRH on h ippocampal neurons.