大鼠外周神经损伤后局部肿瘤坏死因子α在神经病理痛发生中的作用

The role of peripheral nerve TNFα content in the development of neuropathic pain produced by chronic constriction injury of peripheral nerve in rats

目的 通过大鼠坐骨神经慢性压榨伤（CCI）神经病理痛模型热痛敏阈值及坐骨神经中TNFα含量的变化,探讨外周源性TNFα在神经病理痛形成中的作用及可能机制。方法 雌性健康SD大鼠84只,在巴比妥钠麻醉下于大腿中部暴露并结扎坐骨神经。对侧大腿暴露坐骨神经作为模拟对照（Sham）。术后0.5、1、3、5、7、9、11、13、14d测定手术大鼠（n=12）两侧后爪的热痛敏阈值。于术后0.5、1、3、7、10、14d（每时点n=12）处死大鼠,切取两侧坐骨神经片断匀浆。对照组（n=12）标本取自健康大鼠。用酶联免疫法测定TNFα含量及上清液与沉淀物中的相对分布。结果 大鼠热痛敏基础值为（7.9± 0.2）s,大鼠双侧后爪（CCI及Sham）的％MPR在术后 1、3、5、7、9、11d有显著性差异;健康大鼠坐骨神经TNFα含量为（40.62±0.24）pg/mg,CCI侧坐骨神经TNFα含量于术后12h内急剧升高,显著高于Sham侧（P<0.01）,后急剧下降至平台期,但 1、3 d仍高于Sham侧（P<0.05）。Sham侧TNFα含量不同时间点比较及与对照组比较均无显著性差异（P>0.05）。结扎侧坐骨神经TNFα在沉淀物中的相对含量逐渐增加,7d达高峰,后逐渐降低。结论 外周神经源性TNFα是热痛敏产生及维持的主要诱发因素。膜结合型TNFα可能在神经修复中有重要作用。

Objective To investigate the changes in TNFα content of sciatic nerve induced by chronic constriction injury (CCI) of sciatic nerve to determine the role of TNFa in the development of neuropathic pain. Methods Eight-four female health SD rats weighing 250-300g were anesthetized with sodium barbiturate. Unilateral sciatic nerve was exposed and ligated at the middle of thigh. Three ligatures (chromic catgut 4.0) were placed around the sciatic nerve and tied. The distance between the two ligatures was about 1 mm. Sham operation was performed on the contralateral thigh. The sciatic nerve was exposed and mobilized but not ligated. The thermal nociceptive threshold was determined by measuring the withdrawal latency of hindpaw placed on a 58℃ hot plate on days 0.5, 1, 3, 5, 7, 9, 11, 13 and 14 after surgery. Animals were sacrificed on days 0.5, 1, 3, 7, 10 and 14 after surgery. Sciatic nerves were removed from both thighs and frozen at - 80℃ for determination of TNFα content. Sciatic nerve from healthy animals was used as control. The percentage of maximal possible response (% MPR) , was determined for each group (CCI, sham operation, control) % MPR= (new withdrawal latency- average baseline latency)/( 15-average baseline latency) . The distribution of TNFα between supernatant and sediment was also determined. Results The average baseline nociceptive threshold (withdrawal latency) was (7.9±0.2)s. There was significant different in %MPR between the two hindpaws on days 1, 3, 5, 7, 9 and 11 after surgery. The TNFα content of sciatic nerve from healthy rats was (40.62± 0.24) pg/mg protein. The TNFα content of the ligated sciatic nerve was elevated abruptly in 12h after ligation, then abruptly declined to a plateau but was still significantly higher than that of sham-operated side on days 1 and 3. There was no significant difference in TNFα content of sciatic nerve between control group and sham-operation group. The relative content of TNFα content in the sediment of ligated sciatic nerve gradually increased and reached the peak on day 7 and then gradually decreased. Conclusion The TNFα content of peripheral nerves plays an important role in the development of neuropathic pain. Membrane-combined TNFα is involved in the process of nerve repairing.