脊髓背角p38MAPK活化在大鼠神经病理性痛形成中的作用

Activation of p38MAPK in spinal cord dorsal horn following neuropathic pain in rats

目的观察大鼠慢性压迫性损伤（CCI）术后脊髓背角p38丝裂原激活蛋白激酶（p38 MAPK）活化水平的变化,探讨p38MAPK在神经病理性痛形成中的作用。方法SD大鼠70只,随机分为3组：对照组（n=14）、假手术组（n=14）和CCI组（n=42）。结扎大鼠左侧坐骨神经建立CCI模型,通过von Frey纤维测定大鼠神经结扎侧后足缩足反射阈值（MWT）。对照组和假手术组于术后3 d,CCI组于术后3、7、14 d各随机处死8只大鼠,取脊髓背角,采用免疫组化法计数总p38MAPK（t-p38MAPK）和磷酸化p38MAPK（p-p38MAPK）阳性细胞和总细胞,计算阳性细胞率。对照组和假手术组于术后3 d,CCI组于术后3、7、14 d各处死6只大鼠,取脊髓背角,采用Western blot法测定t-p38MAPK和p- p38MAPK蛋白表达水平。结果与对照组和假手术组比较,CCI组各时点MWT降低（P〈0.05或0.01）,t-p38MAPK阳性细胞率和蛋白表达水平差异无统计学意义（P〉0.05）,p-p38MAPK阳性细胞率和蛋白表达水平升高（P〈0.05）。结论外周神经损伤后,脊髓背角p38MAPK活化水平增加,p38MAPK通路激活,可能参与了大鼠神经病理性痛的形成。

Objective To investigate whether the intracellular signal transduction pathway is involved in the mechanisms of neuropathic pain after chronic constrictive injury （CCI） to sciatic nerve, we examine the activation of p38 mitogen-activated protein kinase （p38MAPK） in the dorsal horn of the spinal cord in a rat model of CCI. Methods Seventy male SD rats weighing 160-200 g were randomly divided into 3 groups： （1） normal control group （n = 14）; （2） sham operation group （n = 14） and （3） CCI group （n =42）. The animals were anesthetized with intraperitoneal 1% pentobarbital 30-40 mg/kg. CCI was produced by placing 4 ligatures on the left sciatic nerve at 1 mm intervals with 4-0 chromic catgut. Mechanical withdrawal threshold （MWT） to von Frey filaments was measured on days 3, 7 and 14 after operation. The gait and behavioral changes were observed and recorded every 1-2 days during the 2 weeks after operation. The animals were killed on days 3, 7 and 14 after operation. The lumbar segment （L4, 6 ） of the spinal cord was immediately removed. The activity of p38MAPK in the dorsal horn of the spinal cord was measured by Western blotting and immuno-histochemistry. Results CCI induced dramatic mechanical allodynia from day 3 to day 14 after operation. An increase in the phosphorylation of p38MAPK in the dorsal horn of the spinal cord was also observed after operation. Conclusion Activation of p38mitogen-activated protein kinase may play a major role in the development of neuropathic pain in rats.