大鼠坐骨神经射频热凝神经病理性疼痛模型的建立

A NEUROPATHIC PAIN MODEL INDUCED BY RADIOFREQUENCY ON SCIATIC NERVE IN RATS

摘要:

目的：通过射频热凝损伤大鼠坐骨神经，建立热损伤引起的神经病理性疼痛动物模型。方法：取24只健康成年SD大鼠随机分为四组，假手术组（Sham组）仅进行相关手术操作，RF55组、RF65组和RF75组给予坐骨神经55℃、65℃和75℃射频热凝处理，观察术前、术后1~40 d机械缩足反射阈值（Mechanical Withdrawal Threshold, MWT）和热缩足反射潜伏期（Thermal Withdrawal Latency, TWL）变化，并判断大鼠自发性痛行为和术后运动功能差异，确定最佳造模温度。另取20只大鼠随机分为假手术组（Sham组）和65 ℃射频热凝模型组（RF65组），进行模型复制，术后14 d光镜下观察坐骨神经形态学变化，RT-PCR法测定大鼠L4-L6背根神经节Nav1.8 mRNA表达。结果： RF55组术后3 ~10 d MWT低于术前；TWL术后7~15 d明显缩短。RF65 MWT术后5~30 d降低；TWL术后7~30 d缩短。RF75 MWT术后3~15 d增高；TWL术后均延长。射频热凝组均在术后出现自发性疼痛行为，运动功能评分降低。65℃坐骨神经射频热凝后，组织水肿明显，空泡增多， Nav1.8 mRNA相对表达量明显高于Sham组。结论：大鼠坐骨神经65℃射频热 凝，可以复制稳定的热损伤神经病理性疼痛模型。

Abstract:

Objective: Peripheral nerve injury is the way to create neuropathic pain model. This study is to establish a neuropathic pain model induced by radiofrequency thermal injury of sciatic nerve in rats. Methods: Twenty-four male adult SD rats were randomly divided into four groups. The animals in sham group were received relevant operation, and in other three groups were given with radiofrequency of sciatic nerve at 55℃, 65℃ and 75℃, respectively. The changes of mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) were observed before operation and 1~40 days after radiofrequency. In addition, the spontaneous pain behaviors and the injury of sciatic nerve were assessed. To explore the mechanism of thermal injury, the morphological changes of sciatic nerve and the expression of voltage-gated sodium channel 1.8 (NaV1.8) in L4-L6 dorsal root ganglion in the successful group were further observed. Results: MWT was decreased on 3 days and recovered to original level on 15 days after radiofrequency in RF55. TWL decreased significantly between 7 and 15 days after operation. MWT in RF65 group was increased from 5 days , and recovered to the preoperative level on 35 days after radiofrequency. TWL decreased significantly on the 7 days, and recovered to the preoperative level on the 35 days after operation. MWT in RF75 group was increased 3 days and recovered to the preoperative level 20 days postoperatively. TWL was significantly increased during the observation period. The rats showed self-issuing pain behavior and impaired motor function were showed in three RF groups. The pathological changes in the successfully established group showed nerve edema, loose structure, and increased vacuoles. Nav1.8mRNA of dorsal root ganglion measured by RT-PCR was significantly higher than that in the sham group. Conclusion: Radiofrequency of sciatic nerve at 65℃ can replicate a thermally injured neuropathic pain in rats.