大鼠持续性术后痛形成时脊髓p38MAPK与GRK2的关系

Relationship between p38MAPK and GRK2 in spinal cord in development of persistent postoperative pain in rats

目的评价大鼠持续性术后痛形成时脊髓p38有丝分裂原活化蛋白激酶(p38MAPK)与G蛋白偶联受体激酶2(GRK2)的关系。方法清洁级健康雄性SD大鼠,体重200~250 g,2月龄,取鞘内置管成功的大鼠60只,采用随机数字表法分为6组(n=10):假手术组(S组)、假手术+溶媒二甲基亚砜(DMSO)组(D组)、假手术+GRK2降解抑制剂MDL28170组(M组)、持续性术后痛组(PPP组)、持续性术后痛+DMSO组(PPP+D组)和持续性术后痛+MDL28170组(PPP+M组)。采用皮肤/肌肉切口和牵拉法制备大鼠持续性术后痛模型。于术后即刻、1、2、3 d时,S组和PPP组鞘内注射生理盐水20μl,D组和PPP+D组鞘内注射5%DMSO10μl,M组和PPP+M组鞘内注射MDL2817010μl(50μg),均1次/d。于术前1 d、术后3、7、14、21 d(T1-4)时测定机械缩足反应阈(MWT);于T3行为学测定后各组随机取4只大鼠处死,取L4-6节段脊髓组织,采用Western blot法检测脊髓磷酸化p38MAPK(p-p38MAPK)的表达。结果S组、D组和M组各时点MWT、脊髓p-p38MAPK表达比较差异无统计学意义(P>0.05);与S组比较,PPP组、PPP+D组和PPP+M组MWT降低,脊髓p-p38MAPK表达上调(P<0.05);与PPP组比较,PPP+M组MWT升高,脊髓p-p38MAPK表达下调(P<0.05),PPP+D组MWT、脊髓p-p38MAPK表达差异无统计学意义(P>0.05)。结论脊髓GRK2水平下调可促进p38MAPK活化,参与大鼠持续性术后痛的形成。

Objective To evaluate the relationship between p38 mitogen-activated protein kinase(p38MAPK)and G protein-coupled receptor kinase 2(GRK2)in the development of persistent postoperative pain in rats.Methods Pathogen-free healthy male Sprague-Dawley rats,weighing 200-250 g,aged 2 months,were used in this study.Sixty rats in which intrathecal catheters were successfully implanted were divided into 6 groups(n=10 each)using a random number table method:sham operation group(group S),sham operation plus dimethyl sulfoxide(DMSO)group(group D),sham operation plus GRK2 degradation inhibitor MDL28170 group(group M),persistent postoperative pain group(group PPP),persistent postoperative pain plus DMSO group(group PPP+D)and persistent postoperative pain plus MDL28170 group(group PPP+M).Persistent postoperative pain was evoked by skin/muscle incision and retraction(SMIR).Immediately after operation and at 1,2 and 3 days after operation,normal saline 20μl was intrathecally injected once a day in S and PPP groups,5%DMSO 10μl was intrathecally injected once a day in D and PPP+D groups,and MDL2817010μl(50μg)was intrathecally injected once a day in M and PPP+M groups.The mechanical paw withdrawal threshold(MWT)was measured at 1 day before operation and 3,7,14 and 21 days after operation(T1-4).Four rats in each group were selected after behavioral testing at T3 and sacrificed,and the L4-6 segments of the spinal cord were removed for determination of the expression of phosphorylated p38MAPK(p-p38MAPK)by Western blot.Results There was no significant difference in MWT at each time point or expression of p-p38MAPK among group S,group D and group M(P>0.05).Compared with group S,the MWT was significantly decreased,and the expression of p-p38MAPK was up-regulated in PPP,PPP+D and PPP+M groups(P<0.05).Compared with group PPP,the MWT was significantly increased,and the expression of p-p38MAPK was down-regulated in group PPP+M(P<0.05),and no significant change was found in the MWT or expression of p-p38MAPK in group PPP+D(P>0.05).Conclusion Down-regulated expression of spinal GRK2 can promote the activation of p38MAPK in the spinal cord and is involved in the development of persistent postoperative pain in rats.