截肢前阻断疼痛刺激对大鼠截肢后疼痛及中枢神经系统NMDA受体激活的影响

Effect of pre-amputation pain block on the spinal and anterior cingulated cortex NMDA receptor activation in amputated rats

目的:观察截肢前阻断疼痛刺激对大鼠截肢后痛行为学及中枢神经系统NR2B受体的影响,探讨截肢前阻断疼痛刺激对截肢术后疼痛的影响及其可能机制。方法:成年雄性SD大鼠36只,随机分为截肢前不致痛组(NA组,n=12)、致痛后假阻滞组(PA组,n=12)及致痛后阻滞组(PAB组,n=12)。测量基础值后PA组和PAB组在左后足底皮下注射完全福氏佐剂(complete freund adjuvant,CFA)100μL,NA组在左后足底皮下注射生理盐水100μL。PAB组大鼠于注射后5 d行左坐骨神经阻滞,NA组、PA组大鼠行左坐骨神经假阻滞,阻滞/假阻滞3 d后行左后肢膝上截肢手术。记录注射前、注射生理盐水/CFA后、坐骨神经假阻滞/阻滞后,截肢当天及截肢术后1,3,5,7 d左后足底/左残端的热缩腿反射潜伏期(thermal withdrawal latency,TWL)。截肢后7 d检测大鼠大脑前扣带回皮质(ACC)及脊髓NR2B受体的表达情况。结果:PA组和PAB组大鼠注射CFA后左后足底TWL值明显低于基础值(P<0.05)。截肢前,注射CFA后PA组各时点左后足底TWL值均低于NA组(P<0.05),PAB组阻滞后各时点左后足底的TWL显著高于其致痛后和基础值(P<0.05),并高于NA组和PA组(P<0.05)。与截肢当天残端的TWL值比较,NA组和PAB组于截肢术后第3天开始残端TWL值增高,PA组截肢后各时点残端TWL值与截肢当天的残端TWL值比较,无明显变化。截肢后7 d大脑前扣带回皮质及脊髓NR2B受体阳性细胞:PA组与NA组、PAB组比较显著增多(P<0.05);PAB组与NA组比较差异无统计学意义(P>0.05)。结论:术前患肢的持续性疼痛导致大鼠中枢神经系统NR2B受体的激活,截肢前阻断疼痛刺激能抑制中枢神经系统NR2B受体的激活,阻止术后迁延性疼痛的发生,因而对截肢手术前患肢的疼痛进行合理的镇痛十分必要。

Objective:To investigate the effect of pre-amputation pain block on the N-methyl-D-aspartate receptor activation in the central nervous system of amputated rats,and the association between pre-amputation pain block and chronic amputation-related pain.Methods:Thirty-six adult male SD rats were randomly assigned to an NA group(n=12),a PA group(n=12) and a PAB group(n=12).Group NA was intraplantarly injected saline l00 μL while group PA and group PAB were intraplantarly injected complete Freund adjuvant(CFA) 100 μL.The sciatic nerve of group NA and group PA were freed from surrounding tissue,and that of group PAB was blocked by bupivacaine under pentobarbital sodium anesthesia 5 days after the injection.Thermal withdrawal latency(TWL) was measured before and after the injection.All rats were amputated at the scheduled survival time.The expression of N-methyl-D-aspartate receptor(NR2B) was measured by immunohistochemistry in L4-6 of the spinal cord and the anterior cingulated cortex 7 days after the amputation procedure.Results:The TWL after intraplantar administration of CFA in group PA and group PAB decreased significantly compared with the baseline value(P<0.05),while the saline treated control group remained unchanged.Besides the basic value,the TWL of group PA was shorter than that of group NA at the above-mentioned time-points(P<0.05).Compared with the basic value and group NA,the TWL of group PAB after the block increased significantly(P<0.05).Compared with group NA and group PAB,group PA had a remarkably high expression of NR2B(P<0.05),while there was no difference between group PA and group PAB.Conclusion:Pre-amputation pain may activate N-methyl-D-aspartate receptor of the central nervous system,which may lead acute postoperative pain to chronic pain.It is necessary to treat pre-amputation pain.