title: Role of TRPV1 and ASIC3 channels in experimental occlusal interference-induced hyperalgesia in rat masseter muscle.
abstract: BACKGROUND
  Masticatory muscle pain may occur following immediate occlusal alteration by dental treatment. The underlying mechanisms are poorly understood. Transient receptor potential vanilloid-1 (TRPV1) and acid-sensing ion channel-3 (ASIC3) mediate muscle hyperalgesia under various pathologic conditions. We have developed a rat model of experimental occlusal interference (EOI) that consistently induces mechanical hyperalgesia in jaw muscles. Whether TRPV1 and ASIC3 mediate this EOI-induced hyperalgesia is unknown.
  
  
  METHODS
  Rat model of EOI-induced masseter hyperalgesia was established. Real-time polymerase chain reaction, Western blot and retrograde labelling combined with immunofluorescence were performed to evaluate the modulation of TRPV1 and ASIC3 expression in trigeminal ganglia (TGs) and masseter afferents of rats after EOI. The effects of intramuscular administration of TRPV1 and ASIC3 antagonists on the EOI-induced hyperalgesia in masseter muscle were examined.
  
  
  RESULTS
  After EOI, gene expressions and protein levels of TRPV1 and ASIC3 in bilateral TGs were up-regulated. The percentage of ASIC3- (but not TRPV1-) positive neurons in masseter afferents increased after EOI. More small-sized and small to medium-sized masseter afferents expressed TRPV1 and ASIC3 separately following EOI. These changes peaked at day 7 and then returned to original status within 10 days after EOI. Intramuscular administration of the TRPV1 antagonist AMG-9810 partially reversed this mechanical hyperalgesia in masseter muscle. No improvement was exhibited after administration of the ASIC3 antagonist APETx2. Co-injection of AMG-9810 and APETx2 enhanced the effect of AMG-9810 administration alone.
  
  
  CONCLUSIONS
  Peripheral TRPV1 and ASIC3 contribute to the development of the EOI-induced mechanical hyperalgesia in masseter muscle.
authors.affiliation: Department of Prosthodontics, Peking University School & Hospital of Stomatology, Beijing, China.|Department of Biomedical Sciences, City University of Hong Kong, China.
authors.forename: X X
authors.initials: XX
authors.lastname: Xu
authors.affiliation: Department of Prosthodontics, Peking University School & Hospital of Stomatology, Beijing, China.
authors.forename: Y
authors.initials: Y
authors.lastname: Cao
authors.affiliation: Department of Prosthodontics, Peking University School & Hospital of Stomatology, Beijing, China.
authors.forename: T T
authors.initials: TT
authors.lastname: Ding
authors.affiliation: Center for TMD and Orofacial Pain, Peking University School & Hospital of Stomatology, Beijing, China.
authors.forename: K Y
authors.initials: KY
authors.lastname: Fu
authors.affiliation: Department of Biomedical Sciences, City University of Hong Kong, China.
authors.forename: Y
authors.initials: Y
authors.lastname: Li
authors.affiliation: Department of Prosthodontics, Peking University School & Hospital of Stomatology, Beijing, China.
authors.forename: Q F
authors.initials: QF
authors.lastname: Xie
mesh_terms: D062565:Acid Sensing Ion Channels / Q000378:metabolism*; D000178:Acrylamides / Q000494:pharmacology; D000818:Animals; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D006930:Hyperalgesia / Q000209:etiology / Q000378:metabolism*; D008297:Male; D008406:Masseter Muscle / Q000187:drug effects / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D060888:Real-Time Polymerase Chain Reaction; D050916:TRPV Cation Channels / Q000378:metabolism*; D012668:Trigeminal Ganglion / Q000378:metabolism
chemical_list: C500530:3-(4-t-butylphenyl)-N-(2,3-dihydrobenzo(b)(1,4)dioxin-6-yl)acrylamide; C568269:ASIC3 protein, rat; D062565:Acid Sensing Ion Channels; D000178:Acrylamides; D019086:Bridged Bicyclo Compounds, Heterocyclic; D050916:TRPV Cation Channels; C493922:Trpv1 protein, rat