Effect of ACTH and hydrocortisone on multiple unit activity in the forebrain and thalamus in response to reticular stimulation

ActH injections resulted in a decrease of spontaneous activity and responsiveness in the medial preoptic area, both in normal and adrenalectomized animals, whereas a slight increase of MUA responsivity was found in the fornix and the medial forebrain bundle in response to reticular stimulation.

Abstract

The spontaneous multiple unit activity (MUA) of various brain areas and their responsivity to mesencephalic reticular formation stimulation were studied in chronically implanted, freely moving, intact and adrenalectomized cats. Electrical stimulation of the mesencephalic reticular formation were performed exclusively during slow-wave sleep when the MUA was low and stable. Hydrocortisone resulted in a general decrease of MUA level in the mesencephalic reticular formation, the medial forebrain bundle at the anterior hypothalamic level, the medial preoptic area, the n. centromedianus and the fornix. The responsiveness of the structures to reticular stimulation was much lower in adrenalectomized than in normal animals and this reactivity was further lowered by hydrocortisone injection. ACTH injections resulted in a decrease of spontaneous activity and responsiveness in the medial preoptic area, both in normal and adrenalectomized animals, whereas a slight increase of MUA responsivity was found in the fornix and the medial forebrain bundle in response to reticular stimulation.