title: Orexin-A microinjection into the rostral ventromedial medulla causes antinociception on formalin test.
abstract: Orexins are produced from neurons which are restricted to a few regions of the lateral hypothalamus (LH), where they are important in pain modulation. The orexin receptors and orexinergic projections are localized in regions previously shown to play a role in pain modulation such as rostral ventromedial medulla (RVM). The effect of orexin-A (ORXA) microinjection into the RVM on nociceptive behaviors was examined using the formalin test. Microinjection of ORXA into the RVM, but not adjacent reticularis gigantocellularis (Gi) nucleus, decreased formalin induced nociceptive behaviors. Pretreatment with a selective OX1R antagonist, SB-334867 inhibited the antinociception produced by ORXA, while the administration of SB-334867 alone had no effect. These data demonstrate that ORXA-induced antinociception in the formalin test is mediated in part through orexin1 receptors in the RVM.
authors.affiliation: Department of Basic Sciences, Torbat Heydariyeh University of Medical Sciences, Torbat Heydariyeh, Iran; Department of Physiology, School of Medical Sciences, Tarbiat Modares University, Tehran, Iran.
authors.forename: Hassan
authors.initials: H
authors.lastname: Azhdari-Zarmehri
authors.affiliation: Department of Physiology, School of Medical Sciences, Tarbiat Modares University, Tehran, Iran. Electronic address: ssemnan@modares.ac.ir.
authors.forename: Saeed
authors.initials: S
authors.lastname: Semnanian
authors.affiliation: Department of Physiology, School of Medical Sciences, Tarbiat Modares University, Tehran, Iran.
authors.forename: Yaghoub
authors.initials: Y
authors.lastname: Fathollahi
mesh_terms: D000700:Analgesics / Q000008:administration & dosage*; D000818:Animals; D047908:Intracellular Signaling Peptides and Proteins / Q000008:administration & dosage*; D008297:Male; D008526:Medulla Oblongata / Q000187:drug effects* / Q000502:physiology; D008845:Microinjections; D009479:Neuropeptides / Q000008:administration & dosage*; D000068797:Orexins; D010147:Pain Measurement / Q000187:drug effects* / Q000379:methods; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D000700:Analgesics; D047908:Intracellular Signaling Peptides and Proteins; D009479:Neuropeptides; D000068797:Orexins
keywords: Formalin test; Orexin receptor 1; Orexin-A; Rostral ventromedial medulla