SB203580对神经病理性疼痛早期脊髓γ-氨基丁酸受体亚单位1表达的影响

Effect of SB203580 on γ-aminobutyric acid B receptor 1 expression in spinal cord during early phase of neuropathic pain

目的观察鞘内注射特异性小胶质细胞p38有丝分裂原激活蛋白激酶(MAPK)抑制剂SB203580对神经病理性痛大鼠脊髓背角γ-氨基丁酸受体1[GABAB(1)]表达的影响,探讨脊髓小胶质细胞参与神经病理性疼痛发生的机制。方法成年雄性Sprague-Dawley大鼠32只,全部行鞘内置管,建立L5神经根结扎模型或假手术,按模型和给药方式分为4组,每组各8只。Ⅰ组:神经根结扎+鞘内注射0.1%SB203580[溶于2%二甲亚砜(DMSO)]10μL;Ⅱ组:神经根结扎+鞘内注射溶剂(2%DMSO)10μL;Ⅲ组:假手术+鞘内注射0.1%SB203580(溶于2%DMSO)10μL;Ⅳ组:假手术+鞘内注射溶剂(2%DMSO)10μL。每组于术前1h及术后连续6d经鞘内注射相应药物。分别于术前1h和术后1、3、7d给药前1h测定大鼠的50%机械缩爪阈值(50%PWT),术后第7天完成50%PWT测定后各组取6只大鼠,采用Western印迹法测定脊髓背角GABAB(1)的表达。结果与Ⅱ组相比,Ⅰ组在术后1、3、7d的50%PWT显著升高(P值均<0.01),脊髓背角GABAB(1a)表达显著上调(P值均<0.01);与Ⅳ组相比,Ⅱ组在术后1、3、7d术后50%PWT显著降低(P值均<0.01),脊髓背角GABAB(1a)表达显著下调(P值均<0.01)。各组间GABAB(1b)表达的差异均无统计学意义(P值均>0.05)。结论小胶质细胞可能通过抑制突触前GABAB(1a)表达参与神经病理性疼痛的发生,小胶质细胞抑制剂与GABAB激动剂的联合用药可能成为治疗神经病理性疼痛更有效的方法 。

Objective To investigate the effects of SB203580,an inhibitor of p38 MAPK,on γ-aminobutyric acid B receptor 1 [GABAB（1）] receptor expression in the dorsal horn of a neuropathic pain model,so as to understand the possible mechanism by which the microglia induces neuropathic pain.Methods Thirty-two male adult Sprague-Dawley rats,weighing 200-260 g,were used in this study.Rats were all intrathecally catheterized and assigned to either left lumbar 5（L5） spinal nerve ligation （SNL） or sham surgery,and they were randomly divided into 4 groups （n=8 each）;group Ⅰ SNL＋intrathecal （IT） 0.1%SB203580 10 μL;group Ⅱ SNL＋IT vehicle （2% DMSO） 10 μL;group Ⅲ sham operation＋IT 0.1%SB203580 10 μL;and group Ⅳ sham operation＋IT vehicle （2% DMSO） 10 μL.The 50% Paw withdrawal threshold （50% PWT） to von Frey hair simulation was measured before operation and on the 1st,3rd and 7th day after operation.The GABAB（1） expression in dorsal horn was examined by Western blotting analysis on the 7th day.Results The 50% PWT and the GABAB（1a） expression in the dorsal horn were significantly lower in SNL group than in sham operation group （P0.01）.Intrathecal administration of SB203580 significantly inhibited the SNL-induced mechanical allodynia and increased the GABAB（1a） expression to even higher than the baseline level.Conclusion The mechanisms of neuropathic pain mediated by microglia activation may be related to the inhibition of the pre-synaptic GABAB（1a） receptor activation,which may provide new effective means to treat neuropathic pain.（Shanghai Med J,2010,33：308-311）