Electrical stimulation of the dorsal hippocampus caused a long lasting inhibition of ACTH and adrenocortical responses to photic stimuli in freely moving rats

The effect of a sin-le train of electrical hippocampal stimulation on ACTH and corticosterone (CS) responses to subsequent photic stimulation was stud ied in freely moving male rats. The hippocampal stimulation inhibited the s tress and induced a rise in serum CS levels up to 150 h when compared to sh am stimulated animals. This effect did not exist at 300 h following stimula tion. This sustained hippocampal inhibitory effect on the adrenocortical re sponse, which was not reported previously, was partially abolished by secti on of the dorsal fornix. The present data demonstrate that dorsal hippocamp al stimulation has a long lasting inhibitory effect on pituitary adrenocort ical secretion following neural stimuli and this is partially mediated by t he dorsal fornix. (C) 2001 Elsevier Science B.V. All rights reserved.