盐酸右美托咪定对神经病理性疼痛的作用及其机制

摘要

目的 观察盐酸右美托咪定对大鼠坐骨神经损伤后的镇痛作用,从离子通道角度探讨其机制.方法 ①将Wistar大鼠随机分为4组:0.9％氯化钠溶液+慢性压迫性损伤(CCI)组(N组)、盐酸右美托咪定+CCI组(D组)、ZD7288+ CCI组(Z组)及假手术组(Sham组),每组9只.N组、D组及Z组通过结扎坐骨神经建立神经病理性疼痛模型,Sham组行假手术.术后7d开始,D组腹腔注射盐酸右美托咪定40 μg·kg-1,Z组腹腔注射ZD7288 10 mg·kg-1,N组腹腔注射等体积0.9％氯化钠溶液,每天1次,连续3d.术前、CCI术后7d及给药后3d进行行为学测试,采用Von Frey.纤维测定机械性缩足阈值(PWMT),热辐射法测定缩足潜伏期(TWL).②采用酶解法分离大鼠腰段背根神经节(DRG)细胞,高倍镜下选择中等大小细胞进行全细胞膜片钳记录.结果 CCI术后7d,N组、D组及Z组大鼠右后足PWMT、TWL较术前显著降低(P＜0.05),Sham组大鼠PWMT、TWL与术前比较差异无统计学意义.给药3d后,D组与Z组PWMT、TWL较给药前均明显增加,Z组显著大于D组(P＜0.05);N组给药前后PWMT和TWL无明显变化.电压钳模式下,在DRG细胞内记录到超极化激活的阳离子电流(Lh).盐酸右美托咪定(0.1,1,10 μmol· L-1)可显著降低Ih幅度,使电流幅值从(-844.43±386.34)减少到(-215.99±63.90)pA,对Ih电流抑制率分别为(11.87±1.80)％,(35.26±3.65)％和(52.02±5.56)％,呈浓度依赖性改变(P＜0.05).盐酸右美托咪定使Ih激活曲线左移,半激活电位(V1/2)向超极化方向改变(P＜0.05),但对电流激活曲线的斜率没有影响.结论 盐酸右美托咪定可明显缓解神经病理性疼痛,这可能与其抑制DRG细胞Ih,减少神经元异常放电有关.%Objective To establish neuropathic pain models,explore the effects and mechanisms of dexmedetomidine on neuropathic pain.Methods Wistar rats were randomly divided into four groups (n =9):0.9％ sodium chloride solution CCI group (N),dexmedetomidine CCI group (D),ZD7288 CCI group (Z) and sham-operated group (Sham).Sciatic nerve ligation was performed in group N,D and Z.The sciatic nerve in group Sham was exposured without ligation.7 d after surgery,the rats in group D were intraperitoneal injected with dexmedetomidine (40 μg· kg-1),and the rats in group Z were intraperitoneal injected with ZD7288 (10 mg·kg-1)once a day for 3 d.The same volume of 0.9％ sodium chloride solution was given at the same time in group N.The behavioral test was performed before and 7 d after operation,as well as 3 d after injection treatment.Mechanical allodynia was assessed by paw withdrawal mechanical threshold (PWMT) to von Frey filaments.Thermal hyperalgesia was assessed by paw thermal withdrawal latency (TWL) to radiant heat.Dexmedetomidine block of HCN channels in dorsal root ganglion (DRG) neurons were confirmed by whole-cell recording.Results 7 d after surgery,the PWMT and TWL of rats in group N,D and Z were decreased significantly (P ＜ 0.05).The PWMT and TWL in group Sham were no significant difference before and after operation.Dexmedetomidine significantly increased the levers of PWMT and TWL in group D and Z after treatment for 3 d,and group Z was greater than group D (P ＜ 0.05).Dexmedetomidine (0.1,1,10 μmol· L-1) caused a concentration-dependent decrease in the amplitude of Ih in DRG neurons from (-844.43 ± 386.34) to (-215.99 ± 63.90) pA (P ＜ 0.05),and the inhibition rate of Ih was (11.87 ± 1.80) ％,(35.26 ± 3.65) ％ and (52.02 ± 5.56) ％,respectively(P ＜0.05).Dexmedetomidine produced a dose-related shift to the left of the Ih activation,and a negative shift in V1/2 (P ＜ 0.05).V1/2 shifted from (-86.21 ± 1.68) to (-103.54 ± 2.01) mV (P ＜ 0.05).The slope values were not altered by dexmedetomidine.Conclusion Dexmedetomidine produces a dose-dependently analgesic effect on neuropathic pain after peripheral never injury,which is likely due to the inhibition of Ih and reduction of ectopic spontaneous discharge in DRG neurons.