Regulation of vasopressin and oxytocin release in vitro.

Abstract

Numerous studies have demonstrated a role for vasopressin (VP) and oxytocin (OT) in the regulation of adrenocorticotropin (ACTH) release. Both VP and OT release potentiate the effect of corticotropin releasing factor (CRF) on ACTH release (1), and they are present in portal plasma at the concentration required for this action (2). VP and CRF are co-localized in parvicellular neurons in the paraventricular nucleus which project to the median eminence (3–6), and both of these hormones are released from the isolated median eminence following depolarization (7). Thus, this appears to be one source of VP for regulation of ACTH release. OT is also present in some CRF neurons (8), but it has not been established whether these neurons project to the median eminence. Thus, it is not clear which neurons release OT into the portal circulation, but there are OT fibers in the external zone of the median eminence (9) suggesting a specific projection for control of the anterior pituitary.