EFFECT OF ICV INFUSION OF CRF ON BLOOD-PRESSURE AND ADRENAL-STEROIDS IN RABBITS

The effect of prolonged, 22 h long, intracerebroventricular (i.c.v.) i nfusion of corticotropin-releasing hormone (CRF) on plasma cortisol, c orticosterone and electrolyte concentrations, mean arterial blood pres sure (MAP) and heart rate (HR) were investigated in conscious rabbits. During i.c.v. infusion of CRF, 1 and 3 mu g/h, at a rate of 17 mu l/h , plasma cortisol and corticosterone concentrations rose to the level noted after ACTH stimulation in rabbits. Plasma [Na] did not change, b ut plasma [K] was reduced and plasma osmolality increased during the i nfusion of CRF, 3 mu g/h. MAP and HR, recorded continuously during i.c .v. infusion of CRF, changed only with the higher dose of CRF: MAP was elevated during the first 5 h of infusion, and then returned to the c ontrol level. HR was lower than control at the end of the fi rst hour of infusion and again between 9 and 15 h of infusion. The prolonged ri se of CRF concentration in the brain induced a sustained rise in circu lating adrenal steroid hormones. MAP did not increase to the level not ed after bolus i.c.v. injection of CRF and the rise in MAP was not sus tained.