Effects of dexmedetomidine on activation of c-Jun N-terminal kinase in dorsal root ganglions of rats with neuropathic pain

Objective To evaluate the effects of dexmedetomidine on activation of c-Jun N-terminal kinase (JNK) in the dorsal root ganglions of rats with neuropathic pain (NP).Methods Fifty-four male Wistar rats,weighing 180-220 g,were randomly divided into 3 groups with 18 animals in each group using a random number table:sham operation group (group S),NP group and dexmedetomidine group (group D).The animals were anesthetized with intraperitoneal chloral hydrate.NP was induced by chronic constrictive injury.In group S,the right sciatic nerves were only exposed,but not ligated.In group D,dexmedetomidine 50 μg/kg was intraperitoneally injected immediately after operation once a day for 14 consecutive days.In NP and S groups,the rats received the equal volume of normal saline instead of dexmedetomidine.At 1 day before operation (T0) and 3,7 and 14 days after operation (T1-3),mechanical paw withdrawal threshold (MWT) and thermal paw withdrawal latency (TWL) were measured.The rats in each group were sacrificed after measurement of pain threshold at T1-3 and the ipsilateral dorsal root ganglions of the lumbar segment (L4-6) were removed to detect the phosphorylation of JNK (p-JNK) using immunohistochemistry.Results Compared with group S,MWT was significantly decreased,TWL was shortened,and the expression of p-JNK was up-regulated at each time point after operation in NP and D groups.Compared with group NP,MWT was significantly increased,TWL was prolonged,and the expression of p-JNK was down-regulated at each time point after operation in group D.Conclusion The mechanism by which dexmedetomidine attenuates NP is related to inhibition of activation of JNK in the dorsal root ganglions of rats. Key words: Dexmedetomidine;  Neuropathic pain ;  JNK mitogen-activated protein kinases;  Ganglia, spinal ;  Spinal cord