Vasopressin

Vasopressin (Pituitrin) is a neuropeptide that enhances ACTH secretion by potentiating CRH signaling in the pituitary through V1b receptors coupled to calcium–phospholipid pathways. During chronic stress, vasopressin acts as a crucial regulator of the HPA axis, maintaining corticotroph responsiveness and ACTH release even in the presence of elevated glucocorticoid levels.