Pituitary atrial natriuretic peptide of paraventricular nucleus origin.

Atrial natriuretic peptide-synthesizing neurons in the hypothalamic paraventricular nucleus constitute the major sources of ANP in the three lobes of the pituitary gland. Complete transection of the pituitary stalk eliminated 93% of ANP from the intermediate lobe, 47 and 77% from the anterior and the posterior lobes, respectively. Meantime, increased levels of immunoreactive ANP were measured in the median eminence, due to the accumulation of the peptide in the transected axons centrally to the transected stalk and in the paraventricular nucleus. It is likely that ANP neurons in the paraventricular nucleus innervate the pituitary, but those in the periventricular (median) preoptic nucleus and the organum vasculosum laminae terminalis may not contribute to the ANP innervation of the pituitary gland.