RESERPINE- AND CHLORPROMAZINE-INDUCED CHANGES IN HYPOTHALAMO-HYPOPHYSEAL-ADRENAL SYSTEM IN RATS IN THE PRESENCE AND ABSENCE OF HYPOTHERMIA

¹ The Ohio State University College of Medicine, Department of Pharmacology, Columbus, Ohio

The effects of a single dose of reserpine and chlorpromazine have been studied on various indices of the hypothalamo-hypophyseal-adrenal system in rats. Plasma and adrenal corticosterone concentration, pituitary corticotropin (ACTH) content and corticotropun-releasing factor (CRF) in the median eminence were measured. Both reserpine and chlorpromazine at the dose levels used stimulated the pituitary-adrenal system to cause hypersecretion of ACTH. A marked diminution in the pituitary ACTH content was observed along with depletion of CRF activity in the median eminence of the hypothalamus. Hypothermia was found not to be involved in the endocrine response to these drugs. The role of the biogenic monoamines most abundantly found in the basal hypothalamus was discussed in relationship to the regulation of the release of CRF. It was concluded that reserpine and chlorpromazine produced their effect upon pituitary ACTH secretion by an action upon the neural mechanisms which regulate CRF liberation. It is proposed that monoamines (catecholamines and serotonin) are important as inhibitory neurotransmitters for the physiologic steady-state discharge of CRF from the neuronal terminals in the median eminence of the hypothalamus.