THE ACTH-RELEASING ACTIVITY OF EXTRACTS OF THE POSTERIOR LOBE OF THE PITUITARY IN VIVO1

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Abstract
AGREAT deal of evidence indicates that the release of pituitary adrenocorticotrophin (ACTH) resulting from stress is under neural control. In particular, it appears likely that the hypothalamus constitutes a major pathway for excitation of ACTH release (1). This conclusion has been supported by experiments in which portions of the hypothalamus have either been stimulated or destroyed, resulting in an increase or decrease of ACTH release, respectively (2–7). The precise pathway by which the hypothalamus triggers ACTH release has been the subject of active investigation. A direct secreto-motor innervation of the adenohypophysis appears to be unlikely since the adenohypophysis is possessed of only a scanty innervation at best (8), and section of any direct neural pathway from the hypothalamus fails to block ACTH secretion (9, 10). This leaves a neuro-humoral pathway as the most likely mechanism for nervous control.