title: [Trigeminal purinergic P2X4 receptor involved in experimental occlusal interference-induced hyperalgesia in rat masseter muscle].
abstract: OBJECTIVE
  To explore the expression of purinergic p2X4 receptor (P2X4R) in trigeminal ganglion of rats after occlusal interference. Investigation of peripheral receptor mechanism of occlusal interference-induced masticatory muscle pain will aid the development of drug intervention against this condition.
  
  
  METHODS
  Experimental occlusal interference was established by application of 0.4 mm metal crown to the upper right first molar of male Sprague-Dawley rats. Real-time PCR assay was used to investigate P2X4R mRNA level in trigeminal ganglion in rats with occlusal interference for 3, 7, 10 and 14 days and in control rats without occlusal interference (n=5 in each). Retrograde labelling combining immunofluorescence was performed to evaluate the percentage of P2X4R-positive cells in masseter afferent neurons (n=5 in each group). Graded concentrations of P2XR antagonist TNP-ATP (0.1, 10, 125, 250, 500 μmol/L) or saline (n=5 in each group) was administrated in right masseter and the mechanical sensitivity of bilateral masseters was measured before occlusal interference application, before the injection, and 30 min as well as 60 min after the injection.
  
  
  RESULTS
  Compared with control rats (P2X4R mRNA: right side: 1.00±0.26, left side: 0.94± 0.21; percentage of P2X4R-positive masseter afferents: right side: [64.3±6.3]%, left side: [67.7±5.8]%), the level of P2X4R mRNA in bilateral trigeminal ganglia (right side: 5.98±3.56; left side: 5.06±2.88) of rats with occlusal interference for 7 days up-regulated (P<0.01) and the percentage of P2X4R-positive masseter afferent neurons(right side: [81.7±1.5]%; left side: [82.9±2.3]%) increased (P<0.05). Local administration of 10, 125, 250, 500 μmol/L TNP-ATP increased the mechanical withdrawal threshold in masseter 30 min after injection, compared with those before injection (P<0.05).
  
  
  CONCLUSIONS
  Increased expression of trigeminal P2X4R involves in the development of occlusal interference-induced masseter hyperalgesia.
authors.affiliation: Department of Prosthodontics, Center for Oral and Jaw Functional Diagnosis, Treatment and Research, Peking University School and Hospital of Stomatology, Beijing 100081, China.
authors.forename: Xiaoxiang
authors.initials: X
authors.lastname: Xu
authors.affiliation: Department of Prosthodontics, Center for Oral and Jaw Functional Diagnosis, Treatment and Research, Peking University School and Hospital of Stomatology, Beijing 100081, China.
authors.forename: Ye
authors.initials: Y
authors.lastname: Cao
authors.affiliation: Department of Prosthodontics, Center for Oral and Jaw Functional Diagnosis, Treatment and Research, Peking University School and Hospital of Stomatology, Beijing 100081, China.
authors.forename: Tingting
authors.initials: T
authors.lastname: Ding
authors.affiliation: Center for Temporomandibular Disorders & Orofacial Pain, Peking University School and Hospital of Stomatology, Beijing 100081, China.
authors.forename: Kaiyuan
authors.initials: K
authors.lastname: Fu
authors.affiliation: Department of Prosthodontics, Center for Oral and Jaw Functional Diagnosis, Treatment and Research, Peking University School and Hospital of Stomatology, Beijing 100081, China.
authors.forename: Qiufei
authors.initials: Q
authors.lastname: Xie
mesh_terms: D000255:Adenosine Triphosphate / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D003766:Dental Occlusion; D006930:Hyperalgesia / Q000209:etiology*; D008297:Male; D008406:Masseter Muscle / Q000187:drug effects; D008410:Masticatory Muscles; D058920:Purinergic P2X Receptor Antagonists / Q000008:administration & dosage / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D060888:Real-Time Polymerase Chain Reaction; D058848:Receptors, Purinergic P2X4 / Q000235:genetics / Q000378:metabolism*; D013997:Time Factors; D012668:Trigeminal Ganglion / Q000378:metabolism*
chemical_list: D058920:Purinergic P2X Receptor Antagonists; D012333:RNA, Messenger; D058848:Receptors, Purinergic P2X4; C045674:2',3'-O-(2,4,6-trinitro-cyclohexadienylidine)adenosine 5'-triphosphate; D000255:Adenosine Triphosphate