Corticoliberin activity of rat neurohypophysis is distinct from vasopressin

Electrical stimulation of the neural lobe of the pituitary resulted in an increase of corticosterone secretion in both normal and Brattleboro rats. Bioassaying the corticoliberin (CRF) activity of stalk-median eminence and neural lobe extracts obtained from normal and Brattleboro rats revealed that the endogenous vasopressin was not a prerequisite of ACTH-releasing potency. Arginine-8-vasopressin failed to potentiate the CRF activity of the different extracts. These data suggest that a nonvasopressin substance(s) with CRF activity can be released from the neurohypophysis of the rat, and it may contribute to activating the pituitary-adrenal axis under certain experimental conditions.