title: Facilitation of immunoreactive corticotropin-releasing factor secretion into the hypophysial-portal circulation after activation of catecholaminergic pathways or central norepinephrine injection.
abstract: The functional role of central catecholamines in regulation of ACTH secretion remains controversial. In the present report, the nature of catecholaminergic influences was directly assessed by measurement of hypophysial-portal plasma immunoreactive CRF (irCRF) levels after activation of endogenous aminergic pathways by electrical stimulation or administration of norepinephrine (NE). Electrical stimulation of the ventral noradrenergic ascending bundle, a fiber system primarily carrying catecholaminergic fibers arising from brainstem regions, resulted in a 2.9-fold elevation of portal irCRF levels. Pretreatment with the alpha 1-adrenergic receptor antagonist coryanthine, but not the beta-adrenergic antagonist propranolol, blocked the facilitatory effect of electrical stimulation and reduced prestimulation irCRF levels by 34.7 +/- 4.2% (P less than 0.05). Intracerebroventricular administration of 0.1-5.0 nmol NE resulted in a dose-dependent facilitation of portal plasma irCRF levels which could be blocked by pretreatment with coryanthine. Alternatively, administration of greater than or equal to 5 nmol NE caused a dose-dependent inhibition of irCRF release which could be prevented by pretreatment with propranolol. Finally, irCRF secretion evoked by nitroprusside-induced hypotension was also blocked by pretreatment with coryanthine, but not propranolol. These observations provide strong evidence in favor of a predominantly stimulatory action of NE (and possibly epinephrine) at the hypothalamic level to evoke secretion of CRF and thus to activate the pituitary-adrenal axis.
mesh_terms: D000818:Animals; D002395:Catecholamines / Q000502:physiology*; D003346:Corticotropin-Releasing Hormone / Q000097:blood*; D004558:Electric Stimulation; D007022:Hypotension / Q000139:chemically induced / Q000503:physiopathology; D007031:Hypothalamus / Q000187:drug effects / Q000502:physiology*; D008297:Male; D009434:Neural Pathways / Q000502:physiology; D009599:Nitroprusside; D009638:Norepinephrine / Q000494:pharmacology*; D010286:Paraventricular Hypothalamic Nucleus / Q000502:physiology; D010902:Pituitary Gland / Q000098:blood supply; D011168:Portal System; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D015016:Yohimbine / Q000494:pharmacology
chemical_list: D002395:Catecholamines; D009599:Nitroprusside; D015016:Yohimbine; D003346:Corticotropin-Releasing Hormone; D011433:Propranolol; D009638:Norepinephrine