Central catecholaminergic control of ACTH secretion.

Plasma adrenocorticotropic hormone (ACTH) has been measured after an intra-third ventricular administration of noradrenaline, an adrenergic agonist or an adrenergic antagonist. Centrally administered noradrenaline caused a significant increase in ACTH secretion. The alpha-agonist phenylephrine also increased the ACTH level. However, neither the alpha-antagonist phentolamine nor beta-agonist isoproterenol affected the ACTH level. The beta-antagonist propranolol evoked a significant elevation in ACTH. Passive immunoneutralization was examined with anti-rat corticotropin-releasing factor (CRF) rabbit serum, anti-arginine vasopressin (AVP) rabbit serum and normal rabbit serum (NRS) on the intra-third ventricular noradrenaline-induced ACTH secretion to study the involvement of endogenous CRF. An intra-third ventricular administration of noradrenaline caused a significant increase of ACTH levels in NRS-injected rats and anti-AVP-injected rats, whereas an i.v. anti-rat CRF injection significantly reduced the intra-third ventricular noradrenaline-induced ACTH secretion. These results suggest that central catecholamine stimulated ACTH secretion via the alpha-adrenergic mechanism and that endogenous CRF is at least partly involved in the noradrenaline-induced ACTH secretion.