AbstractIn view of the demonstrated involvement of the hippocampus in the mediation of adrenocortical responses following sciatic nerve stimulation, the role of the septum and the preoptic area in the transmission of this response was investigated. Changes in plasma corticosterone following ether stress and photic, acoustic, or sciatic nerve stimulation were studied in intact rats and in animals with lesions in the medial septal nucleus and the preoptic area. The response to ether stress and to photic and acoustic stimulation was normal in these animals. However, the adrenocortical response to sciatic nerve stimulation was partially reduced in the rats with lesions in the superior, but not in the inferior preoptic area, and it was completely blocked in those with medial septal lesions. Our previous and present experiments indicate that the ventral hippocampus, the fimbria, the septum, and anterior hypothalamic afferents mediate the adrenocortical response to somatosensory stimulation.