神经病理性痛大鼠脊髓背角钾氯共转运体的表达

Expression of potassium-chloride co-transporter in spinal cord dorsal horn after peripheral nerve injury

目的观察左侧坐骨神经分支选择结扎切断(SNI)模型致神经病理性痛大鼠的脊髓背角钾氯共转运体(KCC2)表达的变化。方法将27只健康成年雄性Sprague-Dawley大鼠随机分为SNI组(18只)和假手术组(9只)。SNI组大鼠暴露坐骨神经及其3个末端分支(腓肠神经、腓总神经和胫神经),结扎并切断腓总神经和胫神经,保留腓肠神经完整;假手术组大鼠仅暴露坐骨神经及其分支,不切断。应用vonFrey纤毛检测SNI术后不同时间段的大鼠机械痛阈值;应用免疫印迹技术观察SNI术后不同时间相应的脊髓腰膨大(L4、L5)节段脊髓背角KCC2的表达。结果术后1、3、5、7d,SNI组大鼠左侧后肢的缩足阈值呈显著下降趋势,分别为(3.23±0.49)、(0.60±0.09)、(0.38±0.07)、(0.21±0.06)g,并且在随后的观察期内一直维持在这一低水平。术后1、3、5d,SNI组大鼠腰膨大节段脊髓的左侧背角KCC2的表达量(即KCC2表达量与内参α-tublin表达量的比值)为0.97±0.09、0.32±0.10、0.53±0.15,分别较右侧的1.27±0.08、0.63±0.09、1.11±0.18显著减少(P值均<0.05);术后3d,右侧的表达量为0.63±0.09,较假手术组的1.15±0.13显著下降(P<0.05);至术后7d,脊髓背角两侧KCC2的表达量基本恢复正常水平。结论 SNI模型可致病理性神经痛早期损伤侧脊髓背角KCC2的表达明显减少,可能在慢性神经病理性痛的发展过程中发挥作用。

Objective To investigate the expression of potassium-chloride co-transporter（KCC2）in spinal cord dorsal horn in rat model of neuropathic pain induced by spared nerve injury （SNI）.Methods Twenty-seven adult male SD rats,weighing 200-250 g,were randomly divided into 2 groups：SNI group （n=18）;sham-operation group （n=9）.In the SNI group,the left sciatic nerve of rats and its trifurcations were exposed,and their tibial and common peroneal nerves were tightly ligated and cut distally,while preserving the sural nerve intact.In sham-operated animals,the left sciatic nerve was exposed but not transected.The mechanical withdrawal threshold （MWT） to von Frey filaments was measured 1d before operation and 1 d,3 d,5 d,7 d,14 d,and 21 d post-operation.The animals were sacrificed at 1,3,5,and 7 d after SNI and the lumbar segment of the spinal cord were removed.The expression of KCC2 in the spinal cord dorsal horn （L4,L5） was determined by Western blotting analysis.Results The MWT of the ipsilateral paws in SNI group decreased to （3.23±0.49）,（0.60±0.09）,（0.38±0.07） and （0.21±0.06） g on day 1,3,5,and 7 d after operation,respectively,and then remained unchanged for 21 days after operation.On day 1,3,and 5 d after operation,KCC2 expression in the left spinal cord dorsal horn in the SNI group was significantly lower than that of the right sides （0.97±0.09 vs.0.53±0.15,0.32±0.10 vs.0.63±0.09 and 1.27±0.08 vs.1.11±0.18,all P0.05）.On day 3 after operation the expression in the right side was 0.63±0.09,which was significantly lower than that of the sham-operation group （P0.05）.Conclusion Our results indicate that peripheral nerve injury can induce down-regulation of KCC2 in the dorsal horn of the spinal cord in rats,which may contribute to the development of chronic neuropathic pain.（Shanghai Med J,2010,33：312-315）