title: Orexins/hypocretins acting at Gi protein-coupled OX 2 receptors inhibit cyclic AMP synthesis in the primary neuronal cultures.
abstract: Orexins A and B are newly discovered neuropeptides with pleiotropic activity. They signal through two G protein-coupled receptors: OX(1) and OX(2). In this study, we examined the expression of orexin receptors and effects of the receptors' activation on cyclic AMP formation in the primary neuronal cell cultures from rat cerebral cortex. Both types of orexin receptors were expressed in rat cortical neurons; the level of OX(2)R was markedly higher compared to OX(1)R. Orexin A (an agonist of OX(1)R and OX(2)R) and [Ala(11)-D-Leu(15)]orexin B (a selective agonist of OX(2)R) did not affect basal cyclic AMP formation in the primary neuronal cell cultures. Both peptides (0.001-1 μM) inhibited, in a concentration-dependent manner and IC(50) values in low nanomolar range, the increase in the nucleotide production evoked by forskolin (1 μM; a direct activator of adenylyl cyclase), pituitary adenylate cyclase-activating polypeptide (PACAP27; 0.1 μM), and vasoactive intestinal peptide (VIP; 3 μM). Effects of orexin A on forskolin-, PACAP27-, and VIP-stimulated cyclic AMP synthesis were blocked by TCS OX2 29 (a selective antagonist of OX(2)R), and unaffected by SB 408124 (a selective antagonist of OX(1)R). Pretreatment of neuronal cell cultures with pertussis toxin (PTX) abolished the inhibitory action of orexin A on forskolin- and PACAP-stimulated cyclic AMP accumulation. It is suggested that in cultured rat cortical neurons orexins, acting at OX(2) receptors coupled to PTX-sensitive G(i) protein, inhibit cyclic AMP synthesis.
authors.affiliation: Institute for Medical Biology, Polish Academy of Sciences, Lodowa 106, PL 93-232, Łódź, Poland.
authors.forename: Anna
authors.initials: A
authors.lastname: Urbańska
authors.forename: Paulina
authors.initials: P
authors.lastname: Sokołowska
authors.forename: Agata
authors.initials: A
authors.lastname: Woldan-Tambor
authors.forename: Kaja
authors.initials: K
authors.lastname: Biegańska
authors.forename: Britta
authors.initials: B
authors.lastname: Brix
authors.forename: Olaf
authors.initials: O
authors.lastname: Jöhren
authors.forename: Magdalena
authors.initials: M
authors.lastname: Namiecińska
authors.forename: Jolanta Barbara
authors.initials: JB
authors.lastname: Zawilska
mesh_terms: D000818:Animals; D000242:Cyclic AMP / Q000037:antagonists & inhibitors* / Q000096:biosynthesis*; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism* / Q000502:physiology; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D009479:Neuropeptides / Q000378:metabolism* / Q000502:physiology; D064446:Orexin Receptors; D000068797:Orexins; D061251:Primary Cell Culture; D051381:Rats; D017208:Rats, Wistar; D043562:Receptors, G-Protein-Coupled / Q000502:physiology*; D018013:Receptors, Neuropeptide / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D009479:Neuropeptides; D064446:Orexin Receptors; D000068797:Orexins; D043562:Receptors, G-Protein-Coupled; D018013:Receptors, Neuropeptide; D000242:Cyclic AMP; D019206:GTP-Binding Protein alpha Subunits, Gi-Go