鞘内注射米诺四环素对脊神经结扎大鼠神经病理性疼痛模型的镇痛效应

Analgesic effect of intrathecal Minocycline for neuropathic pain in spinal nerves ligated rats

目的探讨脊髓小胶质细胞参与调解神经病理性疼痛的分子机制。方法成年雄性SD大鼠32只,随机分为4组,每组各8只。假手术(SO)组,暴露脊神经但不结扎;结扎L5/6脊神经(SNL)组;SNL+生理盐水(NS)组结扎L5/6脊神经,鞘内注射NS;SNL+米诺四环素(MI)组,结扎L5/6脊神经,鞘内注射MI。分别测量各组大鼠术前及术后2~7 d机械缩足阈值(MWT)和热痛缩足潜伏期(TWL)。SNL+NS组和SNL+MI组于术后7 d测量痛阈前30 min鞘内注射NS或MI。最后一次痛阈测量后,将大鼠处死取脊髓背角用ELISA法检测脊髓组织肿瘤坏死因子-α(TNF-α)和白介素-1β(IL-1β)表达水平。结果四组大鼠痛阈基础值差异无统计学意义(P>0.05)。SNL组、SNL+NS组和SNL+MI组,术后2~6天MWT和TWL较SO组显著下降(P<0.05)。与SNL组比较,鞘内注射NS对大鼠MWT和TWL无影响(P>0.05);鞘内注射MI显著升高大鼠MWT和TWL(P<0.05)。SNL组脊髓背角TNF-α和IL-1β表达水平较SO组显著升高(P<0.05);SNL+NS组TNF-α和IL-1β表达水平明显高于SO组(P<0.05),与SNL组比较差异无统计学意义(P>0.05);SNL+MI组TNF-α和IL-1β表达水平与SO组比较差异无统计学意义(P>0.05),明显低于SNL组(P<0.05)。结论脊髓小胶质细胞参与调解SNL神经病理性疼痛,鞘内注射米诺四环素的镇痛效应可能与TNF-α、IL-1β密切相关。

Objective To discuss the molecular mechanisms of spinal cord microglia involving in modulating neuropathic pain. Methods 32 aduh male SD rats were randomly divided into 4 groups, each group had 8 rats. Sham operation （SO） group： the spinal nerves were exposed but not ligated; spinal nerves ligated （SNL） group： the L5/6 spinal nerves were exposed and ligated; SNL＋ normal saline （SNL＋NS） group： after SNL neuropathic pain model prepared, rats were received intrathecal injection of NS; SNL＋Minocycline（MI） group： after SNL neuropathic pain model prepared, rats were received intrathecal injection of MI. The thermal withdrawal latency（TWL） and mechanical withdrawal threshold （MWT） were measured before operation and on the 2-7th d after operation. NS or MI. was given at 30 min before measuring pain thresholds on the 7th day after SNL. At the end of the last measuring pain thresholds, rats were sacrificed and the dorsal horn of spinal cords were sampled to detect the expression level of TNF-α and IL-1β by ELISA. Results There was no significant difference in the baseline of pain threshold among rats in 4 groups （P 〉 0.05）. TWL and MWT in SNL group, SNL＋NS group and SNL＋ MI group were significantly lower than those in the SO group on 2-6 d after operation （P 〈 0.05）. Compared to SNL group, intrathecal injection of NS had no effect on MWT and TWL （P 〉 0.05）; intrathecal injection of MI significantly increased the levels of MWT and TWL in rats （P 〈 0.05）. The expression levels of TNF-α and IL-1β in the dorsal horn of spinal cords in SNL group were significantly higher than those in SO group （P 〈 0.05）. The expression levels of TNF-α and IL-1β in SNL＋NS group were significantly higher than those in SO group （P 〈 0.05）, and there was no significant difference between the SNL group and SNL＋NS group （P 〉 0.05）. The expression levels of TNF-α and IL-1β in SNL＋MI group were not significantly different from those in SO group （P 〉 0.05）, and they were significantly lower than those in SNL group （P 〈 0.05）. Conclusion Spinal microglia is involved in mediating SNL neuropathic pain. The analgesic effect of intrathecal injection of Minoeycline may be closely related to TNF-α and IL-1β.