Institution: | aDepartment of Physiology, Division of Integrative Physiology, Jichi Medical School, School of Medicine, Minamikawachi, Tochigi 329-0498, Japan bLaboratory of Molecular Neuropharmacology, Graduate School of Pharmaceutical Sciences, Graduate School of Medicine, Osaka University, Suita, Osaka, Japan |
Abstract: | Pituitary adenylate cyclase-activating polypeptide (PACAP) potentiates both insulin release from islets and insulin action in adipocytes. Therefore, this peptide is considered a regulator of glucose homeostasis. PACAP and its receptors are localized not only in the peripheral tissues but in the central nervous system. The present study examined whether PACAP regulates the feeding behavior and the activity of neurons in the hypothalamic arcuate nucleus (ARC), a feeding center. Food intake was measured in the PACAP knock-out mice. Cytosolic Ca2+ concentration (Ca2+]i) in single neurons isolated from the ARC of rats was measured by fura-2 microfluorometry, followed by immunocytochemical staining with anti-NPY antiserum. PACAP knock-out mice showed a decrease in the intake of high carbohydrate, but not high fat, food. PACAP increased Ca2+]i in NPY neurons of the ARC that are implicated in the feeding, particularly the carbohydrate ingestion. Agonists of PACAP receptors, PAC1-R and VPAC2-R, also increased Ca2+]i. The present study, by demonstrating that PACAP directly reacts with the ARC NPY neurons to increase Ca2+]i and that ingestion of the carbohydrate-rich food is reduced in PACAP-deficiency, suggests a facilitative role for PACAP in the carbohydrate intake. |