RESUMO
Prolactin-releasing peptide (PrRP) was recently isolated from bovine hypothalamus. PrRP is the natural ligand for an orphan G-protein-coupled receptor, hGR3, and directly stimulates prolactin secretion from the anterior pituitary in vitro and in vivo. It has also been reported that PrRP plays an important role as a neurotransmitter and/or neuromodulator in the brain. Although much knowledge has been gained concerning PrRP in the adult rat brain, little attention has been paid to the fetal and postnatal stages. We therefore examined the development of PrRP neurons in the rat brain. In immunocytochemical and in situ hybridization experiments, we observed the transient appearance of PrRP-producing cells in the area postrema (AP), in which PrRP-producing cells do not exist in the normal adult rat. PrRP-producing cells in the AP were detected at P14, and many PrRP-producing cells were observed at P17, though none were detected at P19. This is the first report of the appearance of PrRP-producing cells in the postnatal AP. Our findings suggest that PrRP may play a previously unknown role in the AP of postnatal rats.
Assuntos
Área Postrema/metabolismo , Hormônios Hipotalâmicos/biossíntese , Neuropeptídeos/biossíntese , Animais , Animais Recém-Nascidos , Hormônios Hipotalâmicos/genética , Neuropeptídeos/genética , Hormônio Liberador de Prolactina , Ratos , Ratos WistarRESUMO
Prolactin-releasing peptide (PrRP) was found to be a novel hypothalamic peptide that stimulates prolactin release in vitro and in vivo. In the normal adult rat brain, PrRP neurons are known to be located in only three areas, i.e. the dorsomedial hypothalamic nucleus, ventrolateral reticular formation; and nucleus of the tractus solitarius in the medulla oblongata. These PrRP neurons project neurites into various brain areas, including regions such as the paraventricular nucleus, supraoptic nucleus, and bed nucleus of the stria terminalis. Both PrRP nerve fibers and a high level of PrRP receptor, UHR-1, mRNA are observed in the area postrema (AP),but no PrRP neurons are detected in the AP of normal rats. In this study, we clearly demonstrated that PrRP-producing cells newly appeared in the AP of adrenalectomized rats by in situ hybridization and immunocytochemistry. Our results suggest that PrRP may have some important roles in the AP of adrenalectomized rats. This is the first report demonstrating the appearance of PrRP-positive cells in the AP.
Assuntos
Área Postrema/metabolismo , Hormônios Hipotalâmicos/metabolismo , Neurônios/metabolismo , Neuropeptídeos/metabolismo , Prolactina/metabolismo , Adrenalectomia , Animais , Imuno-Histoquímica , Hibridização In Situ , Hormônio Liberador de Prolactina , RNA Mensageiro/metabolismo , Ratos , Ratos WistarRESUMO
A galanin-like peptide (GALP) was recently isolated as a ligand of GalR2, a galanin receptor subtype. The GALP mRNA is expressed in the arcuate nucleus of the hypothalamus and the posterior pituitary (PP). In this study, we demonstrated the localization of GALP-immunoreactive (-ir) cells in the rat PP. In normal conditions, a few GALP-ir cells were detected in the PP, and these cells increased on dehydration for 4 days. The GALP-immunopositive reaction was dramatically enhanced by the intraperitoneal injection of colchicine. For the identification of GALP-ir cells in the PP, we performed electron microscopic observation, and also double immunocytochemical staining for GALP and S-100 protein. Both studies clearly indicated that the GALP-ir cells in the PP are pituicytes.
