EFFECTS OF DORSAL FORNIX SECTION AND HIPPOCAMPECTOMY ON ADRENOCORTICAL RESPONSES TO SENSORY STIMULATION IN RAT

In order to identify the neural structures which are involved in the mediation of the adrenocortical responses to photic, acoustic and sciatic nerve stimulation, experiments were conducted on male rats with bilateral section of the dorsal fornix and dorsal or ventral hippocampectomies. The basal corticosterone levels in these animals were not significantly different from those in controls. Stimulation of the 3 sensory modalities produced normal adrenocortical responses in rats with fornix section. The hippocampectomies had no effect or only a marginal effect on the response to ether stress and to photic and acoustic stimulation; however, the adrenal response to sciatic stimulation was very significantly reduced. The data demonstrate the participation of the hippocampus in the transmission of somatosensory responses which promote adrenocortical activity. The efferent connections of the hippocampus to the hypothalamus which are involved in this mechanism are discussed.