Involvement Of P2X3 Receptor In Changes Of TMJ Pain Threshold Induced By Occlussal Interferences In Rats

Aims In the present study, the functional significance of P2X3 receptor (P2X3R) in the trigeminal ganglion (TG) and subnuclei caudalis (Vc) in relation to the hyperalgesia of temporomandibular joints (TMJs) induced by occlusal interference was investigated.Methods 60 rats were randomly divided into 5 experimental groups and 5 sham-control groups, and 6 rats in each group. The experimental interference was established by crown application in experimental. On day 1,3,7,14,28 after crown-application, the mechanical pain threshold score was examined by von-Frey filaments. The expression of P2X3R in TGs and Vcs was investigated by immunohistochemistry and real-time PCR.7 days after crown treatment, changes of the mechanical pain threshold score was tested after administration of P2X3R antagonist A-317491 in 6 rats.Results 1) The mechanical pain threshold score of bilateral TMJs significantly increased after occlusal interference and the hyperalgesia persisted for the whole experimental period. The mechanical pain threshold score of both TMJs in experimental group reached the peak on day 7 (p<0.05), and no statistical significance had been found in both sides of TMJs of experimental group.2) The result of immunohistochemistry showed that the proportion of P2X3R-positive cells increased in both sides of TGs and Vcs in experimental groups after crown-application. The proportion of P2X3R-positive cells in TGs peaked on day 7 (p<0.05), while the proportion of P2X3R-positive cells in Vcs peaked on day 3 and persisted to day 7 (p<0.05). No statistical significance had been found in both sides of TGs and Vcs of experimental group.3) The results of real-time PCR showed that expression of P2X3R mRNA significantly increased on day 3 in both sides of TGs (p<0.05). And in Vcs, the expression of P2X3R mRNA peaked on day 1, and statistical significance had been showed on day 1,3,7 (p<0.05).4) The antagonist A-317491 could reverse hyperalgesia caused by occlusal interference.Conclusion It is concluded that the up-regulated expression of P2X3R in TG may contribute to the development of orofacial pain induced by occlusal interference, and P2X3R antagonist may probably be used in treatment of temporomandibular disorders related hyperalgesia.