P2X₃ Receptor Expression And Its Dynamic Changes In The Masseter And Trigeminal Ganglia Of Rats With Masseter Imflammation

Objective:In the present study,the goal is to explore the expression of P2X₃ receptor in the masseter and trigeminal ganglia,the location of the ganglion cell bodys expressing P2X₃ from the peripheral nerve fibres of the masseter in trigeminal ganglia and the dynamic changes of P2X₃ expression in trigeminal ganglia,and to reveal the role of P2X₃ receptor and its mechanism in occurrence and development of masseter chronic imflalnmation after masseter chronic imflammation and interventional treatment so as to offer theoretical and experimental evidence for clinical therapeutic intervention,such as using P2X₃ receptor antagonist to treat masticatory muscle pain.Methods:Twenty-five male SD rats weighing 200-300g were randomly divided into 5 grouds:control,masseter chronic imflammation for 2 days,masseter chronic imflammation for 4 days,masseter chronic imflammation for 6 days and interventional treatment for masseter chronic imflammation.Each group was consist of 5 rats.The rat model of masseter chronic imflammation was established by injection of CFA into the masseter at multipoints.The rats of each group were decapitated 48 hours after the injection of HRP retrograde neural tracing medicine into the masseter through an operation.The rats with masseter chronic ilnflammation subjected to interventional treatment were sacrificed 2 days after the injection of CFA into the masseter at multipoints,followed simutaneously by the injection of PPADS into it at multipoints.The rats with masseter chronic imflammation were valuated by HE staining and their behavior changes.Expression,distribution and location of P2X₃ receptor in the masseter and trigeminal ganglia were determined by HRP retrograde neural tracing technique combined with a double-labeled immunohistochemical technique.Dynamic changes of P2X₃ recetor-positive neurons in trigeminal ganglia after occurence of masseter chronic imflammation and interventional treatment of P2X receptor antagonist were measured and analysed by image analyzer.Results:It was found that less immune-positive nerve fibers of P2X₃ receptor in the masseter existed among muscle fibers of the masseter,and no obvious change in rats with masseter chronic imflammation;P2X₃ neurons in trigeminal ganglia were mainly small neurons, diameters of which were less than 30μm.The HRP-positive neurons and both HRP- and P2X₃ receptor-positive neurons were located at the lateral trigeminal ganglia.The P2X₃-positive neurons and both HRP- and P2X₃ receptor-positive neurons in trigeminal ganglia were significantly increased after CFA-induced masseter inflammation,especially in the inflammation occurence for four days.After using P2X receptor antagonist to treat the masseter chronic imflammation the P2X₃-positive neurons in trigeminal ganglia were apparently less than that of the masseter chronic imflammation rat without any treatment.Conclusions:These results suggest that P2X₃ receptor plays a role in the occurrence and development of the imflammatory pain of masticatory muscle and that it may be applicated as a target of therapeutic intervention for the imflammatory pain of masticatory muscle.