Effect of dexmedetomidine on activity of CREB and c-fos in spinal dorsal horn in a rat model of neuropathic pain / 中华麻醉学杂志

ABSTRACT

Objective To evaluate the effects of dexmedetomidine on the activity of cAMP response element binding protein (CREB) and c-fos in the spinal dorsal horn in a rat model of neuropathic pain.Methods Fifty-four adult male Wistar rats,aged 6-8 weeks,weighing 180-220 g,were randomly divided into 3 groups (n =18 each)sham operation group (group S),chronic neuropathic pain group (group C) and dexmedetomidine group (group D).The animals were anesthetized with intraperitoneal 10％ chloral hydrate 350 mg/kg.The sciatic nerve was exposed and 4 ligatures were placed on the right sciatic nerve at 1 mm intervals with 4-0 silk thread in C and D groups.In group D,dexmedetomidine 50 μg/kg was injected intraperitoneally once a day starting from the end of operation until 1 day before the animals were sacrificed,while the equal volme of normal saline was injected instead of dexmedetomidine in S and C groups.Paw withdrawal threshold to mechanical stimulation with yon Frey filament (MWT) and paw withdrawal latency to thermal stimulation (TWL) were measured on 1 day before operation and 3,7 and 14 days after operation.The animals were sacrificed after measurement of MWT and TWL.Their lumbar segments (L4-6) of the spinal cord were removed for measurement of the expression of phosphorylated CREB (pCREB) and c-fos by immunohistochemistry.Results Compared with group S,MWT was significantly decreased,TWL was shortened,and the expression of pCREB and c-fos was up-regulated on 3,7 and 14 days after operation in C and D groups (P ＜ 0.05).Compared with group C,MWT was significantly increased,TWL was prolonged,and the expression of pCREB and c-fos was down-regulated on 3,7 and 14 days after operation in group D (P ＜ 0.05).MWT was significantly lower,and TWL was shorter on 3,7 and 14 days after operation than on 1 day before operation in C and D groups (P ＜ 0.05).MWT was significantly lower,TWL was shorter,and the expression of pCREB and c-fos was higher on 7 and 14 days after operation than on 3 days after operation in C and D groups (P ＜ 0.05).MWT was significantly higher,TWL was longer,and the expression of pCREB and c-fos was lower on 14 days after operation than on 7 days after operation in C and D groups (P ＜ 0.05).Conclusion The mechanism by which dexmedetomidine reduces neuropathic pain is related to inhibition of the activity of CREB and c-fos in the spinal dorsal horn of rats.