Time course of plasma corticosterone, 18-hydroxycorticosterone and aldosterone concentrations following CRF administration in the rat. A phase of corticosterone inhibition

Synthetic ovine CRF (8 micrograms/rat) injected intravenously in nembutal anaesthetized rats increased not only plasma ACTH and corticosterone but also aldosterone and 18-hydroxycorticosterone concentrations. The maximum elevation occurred 30 min after oCRF administration. 2 h and 4 h after injection the hormone concentrations declined and after 6 h the corticosterone and 18-hydroxycorticosterone values were lower than the corresponding controls. At this time aldosterone remained slightly elevated and ACTH unchanged. 24 h after oCRF injection no difference between the control and oCRF treated animals were evident.