Distribution of prolactin-releasing peptide-immunoreactive neurons in the rat hypothalamus

A newly identified hypothalamic peptide whose specific receptors are present in the anterior pituitary gland is a selective and potent stimulator of prolactin secretion and is therefore termed prolactin-releasing peptide (PRP). We investigated the distribution of PRP-containing neurons in the hypothalamus of female rats by immunocytochemical techniques. Immunocytochemistry using a specific antibody raised to PRP revealed that PRP-immunoreactive perikarya were located in the posteroventral part of the dorsomedial nucleus of the hypothalamus. PRP-immunoreactive nerve terminals were present in high concentrations in a region ventral to the bed nucleus of the stria terminalis, but scarcely observed in the external layer of the median eminence in which well known hypothalamic hormones such as growth hormone-releasing hormone and somatostatin were abundantly detected. This specific distribution in the hypothalamus suggests a novel route of the hypophysiotropic action of PRP.