电针对神经病理性疼痛大鼠损伤处脊髓背角形态及p38MAPK蛋白表达的影响

Effect of electroacupuncture on the morphological changes of the spinal dorsal horn and the expression of p38 mitogen-activated protein kinase in the injured spinal cord of rats with neuropathic pain

目的:观察电针"足三里""昆仑"穴对神经病理性疼痛大鼠损伤处脊髓背角形态及p38丝裂原活化蛋白激酶(p38MAPK)表达的影响。方法:将SD大鼠随机分为假模组、模型组、电针组和药物组,每组10只。采用腰(L)5脊神经结扎法建立神经病理性疼痛大鼠模型。电针组电针术侧"足三里""昆仑"穴30 min,1次/d;药物组予100 mg/mL加巴喷丁溶液(100 mg/kg)腹腔注射,1次/d;两组均于术后1周开始为期1周的干预治疗。分别于造模前及造模后第1、3、5、7、10、12、14天观察并记录大鼠患侧机械缩足反应阈值(MWT)和热缩足反射潜伏期(TWL),并对大鼠受累后肢运动功能进行评分;采用六胺银染色法观察损伤处脊髓背角形态学变化;采用Western blot法检测脊髓L4-L6节段磷酸化(p)-p38MAPK蛋白的相对表达量。结果:与假模组比较,造模后模型组各时点MWT和TWL均显著降低(P<0.001),运动功能评分均显著升高(P<0.001);与模型组比较,电针组和药物组治疗后MWT和TWL显著增高(P<0.05),运动功能评分显著降低(P<0.05)。光镜下可见,模型组神经原纤维增粗扭曲形成缠结,呈焰状,且出现颗粒空泡变性,神经细胞胞质中出现空泡,内含嗜银颗粒;电针组神经原纤维缠结较少,药物组空泡变性减少。与假模组比较,模型组p-p38MAPK蛋白表达明显升高(P<0.001);治疗后,与模型组比较,电针组和药物组p-p38MAPK蛋白表达明显降低(P<0.05)。结论:电针刺激"足三里""昆仑"穴能够提高神经病理性疼痛大鼠的痛阈和受累后肢的运动功能,改善损伤处脊髓背角神经原纤维的坏死,其作用机制可能与降低脊髓背角中p-p38MAPK表达有关。

Objective To investigate the effect of electroacupuncture stimulation at"Zusanli"(ST36)and"Kunlun"(BL60)on the morphological changes of the spinal dorsal horn and the expression of p38 mitogen-activated protein kinase(p38 MAPK)in the injured spinal cord of rats with neuropathic pain.Methods Male Sprague-Dawley rats were randomly divided into sham model group,model group,electroacupuncture group,and medication group,with 10 rats in each group.Spinal nerve ligation of the L5 lumbar vertebra was performed to establish a rat model of neuropathic pain.The rats in the electroacupuncture group were given electroacupuncture at ST36 and BL60 of the operation side with dilatational wave at a frequency of 2 Hz/100 Hz and an intensity of 1.5 mA once a day,30 minutes each time,and those in the medication group were given intraperitoneal injection of 100 mg/mL Gabapentin solution(100 mg/kg)once a day;the one-week intervention was started at one week after surgery.Mechanical withdraw threshold(MWT)and thermal withdrawal latency(TWL)were observed and recorded before modeling and on days 1,3,5,7,10,12 and 14 after modeling,and the motor function of the affected hindlimb was scored.Methenamine silver stain was used to observe the morphological changes of the spinal dorsal horn,and Western blot was used to measure the relative protein expression of p38 MAPK and phospho-p38 MAPK(p-p38 MAPK)in L4-L6 spinal segments.Results Compared with the sham model group,the model group had significant reductions in MWT and TWL at each time point(P<0.001)and a significant increase in motor function score(P<0.001);compared with the model group,the electroacupuncture group and the medication group had significant increases in MWT and TWL and a significant reduction in motor function score after treatment(P<0.05).The model group had obvious neuronal fibrillary tangles,particle vacuolar degeneration,and vacuoles containing argyrophilic grains in the cytoplasm of neural cells under a light microscope,while there were fewer neuronal fibrillary tangles in the electroacupuncture group and reduced vacuolar degeneration in the medication group.Compared with the sham model group,the model group had significant increases in the protein expression of p-p38 MAPK in the spinal dorsal horn(P<0.001),and compared with the model group,the electroacupuncture group and the medication group had significant reductions in the protein expression of p-p38 MAPK in the spinal dorsal horn(P<0.05).Conclusion Electroacupuncture stimulation at ST36 and BL60 can increase pain threshold,improve the motor function of the affected hindlimb,and improve the necrosis of neurofibrils in the spinal dorsal horn in rats with neuropathic pain,possibly by regulating the expression of p-p38 MAPK in the spinal dorsal horn.