Abstract
The effects of Pitressin and synthetic lysine vasopressin on ACTH release were compared in rats with acute hypothalamic lesions, which blocked the response to nonspecific stress. Ascorbic acid depletion in the rats with lesions was the criterion of ACTH release. When the dose was expressed in pressor units, Pitressin and synthetic vasopressin were equipotent in inducing the release of ACTH. It was concluded that the ACTH-releas-ing activity of Pitressin is accounted for by its content of vasopressin and that the results support the hypothesis that vasopressin is the neurohumor stimulating ACTH secretion.