The Hormonal Actions of Corticotropin-Releasing Factor in Sheep: Effect of Intravenous and Intracerebroventricular Injection*

Publisher Website
Google Scholar
Abstract
The 41-residue ovine corticotropin releasing factor (CRF) was administered i.v. and intracerebroventricularly (i.c.v.) to merino sheep. A significant rise in plasma ACTH, .beta.-lipotropin (.beta.LPH) and cortisol was demonstrated after the administration of 200 .mu.g, i.v. A highly significant correlation between the increments in plasma ACTH and .beta.LPH was observed. The plasma ACTH rise was evident within 5 min and was abolished by the prior administration of 0.4-4.0 mg dexamethasone. No significant rise in plasma GH [growth hormone], LH [luteinizing hormone], PRL [prolactin], insulin, glucagon, pancreatic polypeptide, met-enkephalin, angiotensin II, aldosterone or vasopressin could be demonstrated. Although smaller doses of CRF (50 ng to 5 .mu.g) were effective when given i.c.v., the ACTH response was more delayed. CRF stimulates a rapid increase in the secretion of ACTH and .beta.LPH in sheep. Suppression of this response by dexamethasone indicates that glucocorticoids are capable of acting on the pituitary to inhibit the ACTH response to CRF. The delayed response when CRF is given i.c.v. may be due to diffusion. The action of CRF appears to be relatively specific, in that the plasma concentrations of the other pancreatic, pituitary and adrenal hormones measured were not affected.