Adrenocortical responses to corticotropin-releasing factor in the rat.
The time course of plasma corticosterone was measured in male Sprague-Dawley rats whose endogenous release of ACTH had been blocked following rapid i.v. injections of doses ranging from 0.003 to 10 micrograms corticotropin-releasing factor (CRF) per rat and during i.v. infusions at rates ranging from 0.001 to 20 ng CRF X min-1 X 100 g body weight-1. The range of the dose-response curve, following rapid injection, extends from 0.01 to 0.37 micrograms CRF, whereas it extends over a 20 000-fold range from 0.001 to 20 ng CRF X min-1 X 100 g body weight-1 during a continuous infusion. The delayed response to a small rate of CRF could be ascribed to a relatively long time of residence of CRF in the plasma which implies that a relatively long period of time is required until a minimal plasma CRF concentration is reached after the onset of a continuous infusion of CRF at a small rate. When presented with a prolonged infusion of CRF at a large rate, the pituitary secretion of ACTH is rapidly turned on at a rate which exhibits the characteristics of a prolonged secretion at a constant large magnitude.
D000302:Adrenal Cortex / Q000187:drug effects* / Q000378:metabolism; D000324:Adrenocorticotropic Hormone / Q000378:metabolism; D000818:Animals; D003345:Corticosterone / Q000097:blood; D003346:Corticotropin-Releasing Hormone / Q000494:pharmacology*; D007263:Infusions, Parenteral; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains
D000324:Adrenocorticotropic Hormone; D003346:Corticotropin-Releasing Hormone; D003345:Corticosterone