背根神经节微量注射7-硝基吲唑抑制炎症性疼痛

Suppression of inflammatory pain by microinjecting 7-nitroindazole into dorsal root ganglion

目的:观察完全弗氏佐剂(complete Freund’s adjuvant,CFA)诱导炎症性疼痛的现象,并探究背根神经节(DRG)部位注射神经元型一氧化氮合酶(neuronal nitric oxide synthase,nNOS)抑制剂7-硝基吲唑(7-nitroindazole,7-NI)对于炎症性疼痛是否有镇痛作用并简要探讨其镇痛机制。方法:小鼠足底注射10μl CFA诱导炎症性疼痛动物模型,使用von Frey纤维丝采用up-and-down的方法测定小鼠的50%足底回缩阈值(50%paw withdrawal threshold,50%PWT)作为痛觉行为学的评价指标。在小鼠的背根神经节部位微量注射10μg 7-NI观察50%PWT的变化情况。用免疫印迹的方法观察炎症相关的降钙素基因相关肽(calcitonin gene related peptide,CGRP)在CFA诱导模型后、造模后给予7-NI和nNOS基因敲除小鼠造模后的表达情况。结果:与DMSO组相比,7-NI组造模后2～12 h 50%PWT显著升高。观察到CGRP的表达量在CFA诱导后增加,而在给予7-NI和nNOS基因敲除组内CGRP的表达增加可以被逆转。结论:小鼠DRG部位注射7-NI对炎症性疼痛具有镇痛作用,且炎症性疼痛中CGRP表达量的增加可能是一氧化氮(nitric oxide,NO)在DRG内起疼痛敏感性作用的下游机制。

Objective：To observe the phenomenon of complete Freund＇s adjuvant（CFA）-induced inflammatory pain and explore the analgesic effect of 7-nitroindazole（7-NI） on dorsal root ganglion（DRG）,and briefly discuss its analgesic mechanism.Methods：Ten microliters of CFA were injected into the plantar surface of the hind paw of the mice to produce inflammatory pain models,von Frey filaments were used to determine 50% paw withdrawal threshold（PWT） adopting by up-and-down method which can be regarded as an evaluation criteria for the pain behavior test.The changes of 50% PWT were tested by microinjecting 10 μg 7-NI into DRG of the mice.Detect the expression of calcitonin gene related peptide（CGRP） in CFA-induced,7-NI treated and neuronal nitric oxide synthase（nNOS） knock-out models by Western blot.Results： Compared with DMSO group,50% PWT significantly increased in 7-NI group during 2～12 h after CFA inducing.The expression of CGRP increased after CFA injection,this effect could be reversed by 7-NI administration or nNOS knock-out.Conclusion： Microinjection of 7-NI into DRG could produce analgesia in inflammatory pain mice.Increased expression of CGRP might be the downstream mechanism resulted from NO mediated nociceptive effect in dorsal root ganglion.