脊髓刺激术对神经病理性痛模型大鼠痛行为和脊髓背角内小胶质细胞激活的影响

目的:探讨脊髓刺激术(spinal cord stimulation,SCS)对神经病理性痛(neuropathic pain,NP)模型大鼠痛行为及脊髓背角内小胶质细胞激活的影响。方法:成年大鼠20只,随机分为4组:(1)正常对照组(control组);(2)SCS组:正常大鼠给予SCS刺激;(3)脊神经结扎(spinal nerve ligation,SNL)假刺激组(SNL+shamSCS组):SNL且植入SCS装置,但不刺激;(4)SNL+SCS组:SNL且给予SCS刺激。术前连续3 d、术后第5 d检测各组大鼠足底机械痛敏阈值(mechanical withdrawal threshold,MWT)。SCS组和SNL+SCS组术后第2-5 d给予SCS刺激,每d持续8 h;且在每次给予SCS 8 h刺激前进行90 min行为学测试,即SCS刺激30 min,以及刺激结束后的60 min内(共90 min),每15 min测量一次MWT。在第5 d给予SCS 8 h刺激结束后处死动物,利用免疫组织化学染色结合平均光密度(average optical density,AOD)分析的方法检测各组大鼠腰5节段脊髓背角内小胶质细胞特异性标志物OX-42的表达情况。结果:(1)行为学结果显示:术后第5 d,SNL+shamSCS组和SNL+SCS组大鼠手术侧后爪的MWT由术前26.00±0.0 g分别降至5.50±0.96 g和6.40±0.40 g(P<0.05);SNL+SCS组给予SCS刺激30 min后大鼠手术侧后爪的MWT明显有所提高,达16.20±2.60 g,与刺激前(6.40±0.40 g)相比有显著性差异(P<0.05);但停止SCS刺激60 min后,大鼠的MWT明显有所下降,与刺激前几乎没有明显差别。(2)免疫组化染色结果显示:术后第5 d,SNL+SCS组脊髓背角内OX-42的表达明显弱于SNL+shamSCS组,但二者都强于control组和SCS组;AOD结果也证实:SNL+SCS组大鼠脊髓背角内OX-42的AOD(1.29±0.28)明显低于SNL+shamSCS组(2.66±0.38),但仍高于control组(0.14±0.21)和SCS组(0.24±0.08)。结论:SCS对SNL模型大鼠的神经病理性痛有较好的镇痛效果;该作用可能与SCS刺激显著抑制脊髓背角内小胶质细胞的激活密切相关。

The effect of spinal cord stimulation on pain behavior and activition of microglia in spinal dorsal horn of rats with neuropathic pain

Objective:To investigate the effect of spinal cord stimulation(SCS) on pain behavior and activition of microglia in spinal dorsal horn of rats with neuropathic pain(NP).Methods: 20 adult rats were randomly divided into 4 groups:(1) control group;(2) SCS group: normal rats with SCS;(3) SNL+shamSCS group:the SCS device was implanted but without SCS;(4) SNL+SCS group: SNL rats with SCS.Mechanical withdrawal threshold(MWT) was detected for 3 consecutive days pre-operation and on the 5 d post-operation.Rats in SCS and SNL+SCS groups received SCS during 2-5 d after the operation,8 hours each day.Besides,both of SCS group and SNL+SCS group were given a 90 min test before 8 hours SCS,which meant that SCS was applied for 30 min and the withdrawl thresholds of the ipsilateral hind paw were assessed at time of 0,15,30,45,60 and 90 min.After SCS on the 5 d of post-operation,rats were sacrificed.Immunohistochemistry combined with average optical density(AOD) analysis was performed to examine the expression of OX-42(marker of microglia) in the L5 segment spinal dorsal horn of rats of all 4 groups.Result:(1) The behavior results showed that the MWT in SNL+shamSCS group and SNL+SCS group reduced significantly from 26.00±0.0 g pre-operation to 5.50±0.96 g and 6.40±0.40 g respectively on the 5 d of post-operation(P<0.05).Significantly elevation of MWT,from 6.40±0.40 g pre-SCS to 16.20±2.60 g,was observed after 30 min SCS for the SNL+SCS group(P<0.05).What ’ s more,30 min after cessation of SCS,the MWT decreased obviously to the pre-SCS level.(2)Immunohistochemical results demonstrated that on the 5 d of postoperation,the expression of OX-42-immunoreactivity in SNL+SCS group was more lower than SNL+shamSCS group,but both of them showed more immunoreactivity than control group and SCS group.The results of AOD analysis also showed that the spinal dorsl horn AOD of SNL+SCS group(1.29±0.28)was remarkably lower than SNL+shamSCS group(2.66±0.38,P<0.05),but still higher than control group(0.14±0.21)and SCS group(0.24±0.08).Conclusion: SCS had remarkable analgesic effect on SNL induced NP of rats;the underlying mechanism for the effect might be closely related to the inhibition of the acivition of the microglia in spinal dorsal horn.