Corticotropin releasing hormone (CRH) stimulates pituitary ACTH secretion through type-1
CRH (CRH1) receptors. Stimulation of the hypothalamic pituitary adrenal (HPA) axis as well
as increased corticotroph responsiveness during stress and adrenalectomy are associated
with marked pituitary CRH binding downregulation. The presence of CRH1 receptors in the
pituitary are essential to maintain ACTH secretion. Downregulation of CRH binding is
associated with normal or elevated levels of CRH1 receptor mRNA and this may contribute …

The physiological regulation of ACTH secretion is largely dependent on the interactive
effects of CRH and vasopressin (VP) in the pituitary corticotroph. The importance of the
magnocellular and parvicellular hypothalamic systems as a source of VP for pituitary
regulation was studied by analyzing the effects of endogenous activation of these systems or
VP infusion on the ability of CRH to regulate its receptor sites in the anterior pituitary. CRH
receptors were measured by binding of [125I] Tyr-ovine CRH to membrane-rich fractions of …