Effect Of Dexmedetomidine On Expression Of P2X₄Urinergic Receptor And P38Mitoeen-Activated Protein Kinases MRNA In A Rat Model Of Chronic Neuropathic Pain

Objective:To investigate the effect of dexmedetomidine on expression of P2X4purinergic receptor(P2X4R) and p38Mitogen-Activated Protein Kinases(P38MAPK) mRNA in a rat model of chronic neuropathic pain, evaluate the effect of neuropathic pain with dexmedetomidine to provide the new method and basis for treatment.Methods:seventy-two male SD rats weighing180～220g were randomly assigned into3groups (n=24each):sham operation group (group S), neuropathic pain group (group NP) and dexmedetomidine group (group Dex). In group S, the right sciatic nerves were exposed but not ligated, and in other groups four ligatures were placed around the right sciatic nerve(chronic constriction injury of sciatic nerve, CCI) according to Bennett’s method. From the instant after operation, the rats of group Dex were injected intraperitoneally with dexmedetomidine50μg/kg daily after CCI, while the same volume normal saline was injected into group S and group NP. Mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) were texted on the day before operation and the1st,3rd,7th,14th d after operation. Six animals were randomly killed on the1st,3rd,7th,14th d after CCI following the measurement of pain threshold in each group, the L4-6segments of spinal cords were removed for determination of P2X4R and p38MAPK mRNA expression by reverse transcription-polymerase chain reaction (RT-PCR).Results:Compared with group S, MWT and TWL were significantly decreased and the expression of P2X.(?)R and p38MAPK mRNA were significantly up-regulated after operation in group NP and Dex (P<0.05). Compared with group NP. TWL and MWT were significantly increased and the expression of P2X4R and p38MAPK mRNA were significantly down-regulated after operation in group Dex (P<0.05). On the7th d after operation, TWL and MWT of group NP and group Dex were significantly decreased and the expression of P2X1R and p38MAPK mRNA were significantly up-regulated compared with those on thelst,3rd,14th d after operation (P<0.05).Conclusion:Dexmedetomidine can visibly attenuate chronic neuropathic pain of rats through inhibition of the expression of P2X4R and p38MAPK.