持续激活脊髓代谢型谷氨酸受体4对神经病理性痛大鼠痛觉过敏的影响:与Gαi的关系

Effect of continuous activation of spinal metabotropic glutamate receptor 4 on hyperalgesia in a rat model of neuropathic pain:relationship with Gαi

目的评价持续激活脊髓代谢型谷氨酸受体4(mGluR4)对神经病理性痛大鼠痛觉过敏的影响及其与抑制性G蛋白α(Gαi)的关系。方法清洁级健康雄性成年SD大鼠,体重200~250 g,取鞘内置管术成功的大鼠41只,采用随机数字表法分为4组:假手术组(Sham组,n=8)、假手术+mGluR4正性变构调节剂VU0155041组(Sham+V组,n=8)、神经病理性痛组(NP组,n=8)和神经病理性痛+VU0155041组(NP+V组,n=17)。采用脊神经根结扎(SNL)方法建立大鼠神经病理性痛模型。于SNL后第7天,Sham+V组和NP+V组鞘内注射VU0155041500 nmol,10μl,2次/d,连续7 d;Sham组和N注射等容量生理盐水。于SNL前、SNL后第7天、每次鞘内注射前后30 min、末次鞘内注射后24 h时测定50%缩足反应阈(PWT)。NP+V组于SNL前、SNL后第7天和末次鞘内注射后24 h时采用Western blot法检测脊髓mGluR4、Gαi1、Gαi2、Gαi3的表达。结果与Sham组比较,NP组和NP+V组SNL后第7天和末次鞘内注射后24 h时PWT降低(P<0.05);与NP组比较,NP+V组末次鞘内注射后24 h时PWT升高(P<0.05)。与SNL后第7天时比较,NP+V组末次鞘内注射后24 h时PWT升高(P<0.05),NP组差异无统计学意义(P>0.05)。与给药前比较,NP+V组每次鞘内给药后PWT均升高(P<0.01)。与SNL前比较,NP+V组SNL后第7天脊髓mGluR4和Gαi3表达下调(P<0.05);与SNL后第7天时比较,NP+V组末次鞘内注射后24 h时脊髓mGluR4和Gαi3表达上调(P<0.05)。结论持续激活脊髓mGluR4可减轻神经病理性痛大鼠已形成的痛觉过敏,机制可能与Gαi3有关。

Objective To evaluate the effect of continuous activation of spinal metabotropic glutamate receptor 4(mGluR4)on hyperalgesia in a rat model of neuropathic pain(NP)and the relationship with inhibitory G proteinα(Gαi).Methods Clean-grade healthy adult male Sprague-Dawley rats,weighing 200-250 g,were used in this study.Forty-one rats in which intrathecal catheters were successfully inserted were selected and divided into 4 groups using a random number table method:sham operation group(Sham group,n=8),sham operation plus mGluR4 positive allosteric modulator VU0155041 group(Sham+V group,n=8),NP group(n=8),and NP plus VU0155041 group(NP+V group,n=17).The model of NP was established by spinal nerve ligation(SNL)in anesthetized rats.On day 7 after SNL,VU0155041500 nmol(10μl)was intrathecally injected,twice a day,for 7 consecutive days in Sham+V and NP+V groups,whereas normal saline was used as vehicle control in Sham and NP groups.The 50%paw withdrawal threshold(PWT)was measured before SNL,on day 7 after SNL,at 30 min before and after each intrathecal injection,and at 24 h after the last intrathecal injection.The expression of mGluR4,Gαi1,Gαi2 and Gαi3 in the spinal cord was detected by Western blot before SNL group and on day 7 after SNL and at 24 h after the last intrathecal injection in NP+V group.Results Compared with Sham group,the PWT was significantly decreased on day 7 after SNL and at 24 h after last intrathecal injection in NP group and NP+V group(P<0.05).Compared with NP group,the PWT was significantly increased at 24 h after last intrathecal injection in NP+V group(P<0.05).Compared with that on day 7 after SNL,the PWT was significantly increased at 24 h after the last intrathecal injection in NP+V group(P<0.05),and no significant change was found in NP group(P>0.05).The PWT was significantly increased after each intrathecal administration as compared with that before administration in NP+V group(P<0.01).The expression of mGluR4 and Gαi3 in the spinal cord was significantly up-regulated on day 7 after SNL compared with that before SNL in NP+V group(P<0.05),and was increased at 24 h after the last intrathecal injection compared with that on day 7 after SNL(P<0.05).Conclusion Continuous activation of spinal mGluR4 can reduce the hyperalgesia in a rat model of NP,and the mechanism may be related to Gαi3.