Hypothalamic atrial natriuretic peptide and secretion of oxytocin

Our study corroborated previous findings on the distribution of ANP and co-localization of ANP and OT in hypothalamic magnocellular neurons. We detected ANP/OT in smaller cells which apparently corresponded to parvocellular neurons and additionally a massive group of ANP immunoreactive fibers from periventricular regions to the median eminence, here closely associated with oxytocinergic fibers originated from PVN. ANP immunoneutralization did not change the basal OT level but blocked the OT secretion normally induced by osmotic stimulus. Thus, endogenous hypothalamic ANP seems necessary to stimulate OT release in the hyperosmolality condition.