“Inhibition” of Pituitary Acth Release After Administration of Reserpine or Epinephrine1

Acute release of ACTH, as measured by changes in concentration of adrenal ascorbic acid, was stimulated in the rat by a single injection of reserpinc or epinephrine. Prolonged hypersecretion of ACTH, as measured by changes in adrenal weight, and depletion of pituitary ACTH content followed repeated injections of either substance. On the other hand, the acute release of ACTH in response to the stress of ether anesthesia was found to be diminished or absent after a single injection of epinephrine or after multiple injections of either reserpine or epinephrine. These data are consistent with the hypothesis that the amount of pituitary ACTH available for immediate release in response to acute stress is reduced after administration of reserpine or epinephrine, whereas chronic hypersecretion of ACTH remains unimpaired.