title: Involvement of temporomandibular joint P2X3 and P2X2/3 receptors in carrageenan-induced inflammatory hyperalgesia in rats.
abstract: The aim of this study was to investigate the role of P2X3, P2X2/3 and P2X7 receptors in the development of TMJ hyperalgesia induced by carrageenan. We also investigated the expression of mRNA of P2X7 receptors in the trigeminal ganglia and the existence of functional P2X7 receptors in the rat's TMJ. The P2X1, P2X3 and P2X2/3 receptor antagonist TNP-ATP, but not the selective P2X7 receptor antagonist A-438079, significantly reduced carrageenan-induced TMJ inflammatory hyperalgesia. The qPCR assay showed that mRNA of P2X7 receptors are expressed in the trigeminal ganglia but this expression is not increased by the inflammation induced by carrageenan in the TMJ region. The P2X7 receptor agonist BzATP induced TMJ inflammatory hyperalgesia that was significantly reduced by pretreatment with dexamethasone. These results indicate that P2X3 and P2X2/3 but not P2X7 receptors are involved in carrageenan-induced TMJ inflammatory hyperalgesia. However, functional P2X7 receptors are expressed in the TMJ region. The activation of these receptors by BzATP sensitizes the primary afferent nociceptors in the TMJ through the previous release of inflammatory mediators. The findings of this study point out P2X3 and P2X2/3 receptors, but not P2X7 receptors, as potential targets for the development of new analgesic drugs to control TMJ inflammatory pain.
authors.affiliation: Department of Physiological Sciences, Laboratory of Orofacial Pain, Piracicaba Dental School, State University of Campinas - UNICAMP, Piracicaba, Sao Paulo, Brazil.
authors.forename: Juliana Maia
authors.initials: JM
authors.lastname: Teixeira
authors.forename: Maria Cláudia G
authors.initials: MC
authors.lastname: Oliveira
authors.forename: F H
authors.initials: FH
authors.lastname: Nociti
authors.forename: J T
authors.initials: JT
authors.lastname: Clemente-Napimoga
authors.forename: Adriana
authors.initials: A
authors.lastname: Pelegrini-da-Silva
authors.forename: Carlos Amílcar
authors.initials: CA
authors.lastname: Parada
authors.forename: Cláudia Herrera
authors.initials: CH
authors.lastname: Tambeli
mesh_terms: D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D002351:Carrageenan; D006930:Hyperalgesia / Q000139:chemically induced / Q000378:metabolism*; D007249:Inflammation / Q000378:metabolism; D008297:Male; D058911:Purinergic P2X Receptor Agonists / Q000494:pharmacology; D058920:Purinergic P2X Receptor Antagonists / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017208:Rats, Wistar; D018048:Receptors, Purinergic P2 / Q000096:biosynthesis / Q000502:physiology*; D058476:Receptors, Purinergic P2X2 / Q000096:biosynthesis / Q000502:physiology; D058477:Receptors, Purinergic P2X3 / Q000096:biosynthesis / Q000502:physiology; D058486:Receptors, Purinergic P2X7 / Q000096:biosynthesis / Q000502:physiology; D013704:Temporomandibular Joint / Q000187:drug effects / Q000378:metabolism*; D013777:Tetrazoles / Q000494:pharmacology; D012668:Trigeminal Ganglion / Q000187:drug effects / Q000378:metabolism
chemical_list: C523668:3-(5-(2,3-dichlorophenyl)-1H-tetrazol-1-yl)methylpyridine; D058911:Purinergic P2X Receptor Agonists; D058920:Purinergic P2X Receptor Antagonists; D011725:Pyridines; D012333:RNA, Messenger; D018048:Receptors, Purinergic P2; D058476:Receptors, Purinergic P2X2; D058477:Receptors, Purinergic P2X3; D058486:Receptors, Purinergic P2X7; D013777:Tetrazoles; C033901:3'-O-(4-benzoyl)benzoyladenosine 5'-triphosphate; C045674:2',3'-O-(2,4,6-trinitro-cyclohexadienylidine)adenosine 5'-triphosphate; D000255:Adenosine Triphosphate; D002351:Carrageenan