不同时间脉冲射频对神经病理性疼痛大鼠模型下丘脑β-内啡肽的影响

Effects of pulsed radiofrequency with different treatment times on the beta-endorphin in hypothalamus in a rat model of chronic neuropathic pain

目的观察不同时间脉冲射频（PRF）作用于慢性坐骨神经压迫损伤（CCI）大鼠模型下丘脑β-内啡肽含量的影响。方法雄性SD大鼠72只，随机分成4组：假PRF治疗组（A0组），120sPRF治疗组（A1组），480sPRF治疗组（A2组），720SPRF治疗组（A3组），每组18例。建模后7d，对PRF组坐骨神经结扎处近端进行PRF干预治疗，脉宽20ms，脉冲频率2Hz，电压55v，治疗持续时间分别为120s，480S，720s；假PRF治疗组，在PRF治疗组坐骨神经相同位置处只放置射频电极针，但不给予通电治疗。PRF治疗后7、14、21d时，每组各时间点分别处死6只大鼠，取下下丘脑，用酶联免疫法测定不同时间点下丘脑中β-内啡肽的浓度，光镜下观察大鼠坐骨神经组织学变化。结果PRF治疗组在治疗后7、14d时，与假PRF治疗组比较大鼠下丘脑β-内啡肽含量明显升高（P〈0．01）。治疗后14d时，A3组和A2组明显高于A1组（P〈0．05）；治疗后21d时，A3组高于A2组（P〈0．05），A2组高于A1组（P〈0．05）。在光镜观察下与假PRF治疗组比较，经PRF干预后的坐骨神经结构变化轻微，而且随着时间延长呈恢复趋势。结论作用时间为120、480、720S的脉冲射频均可引起CCI大鼠下丘脑β-内啡肽含量明显升高。适当增加脉冲射频的作用时间，会在更长时间内使CCI大鼠下丘脑的β-内啡肽维持较高的浓度，可能延长脉冲射频镇痛时间。

Objective To observe the effects of pulsed radiofrequency with different treatment times on the beta-endorphin in hypothalamus in a rat model of chronic neuropathie pain. Methods Seventy-two male SD rats weighing 200-220 g were randomly divided into 4 groups （n=18 in each group）： sham PRF group （A0）, PRF 120 s group （A1）, PRF 480 s group （A2）, PRF 720 s group （A3）. Neuropathic pain was induced by chronic constrictive injury （CCI）. PRF intervention was performed on the proximal part of the sciatic nerve ligation in group PRF at 7 d after CCI, with pulse duration 20 ms, pulse frequency 2 Hz, voltage 55 V, and the duration of treatment was 120 s, 480 s, 720 s respectively. The radiofrequency electrodes were placed at the same position of the sciatic nerve without electricity applied in sham PRF group. The expression of beta-endorphin by enzyme-linked immunosorbent assay （ELISA） was respectively measured in the hypothalamus in each group （n=6） at 7, 14, 21 d after PRF treatment and the histological changes of the sciatic nerve in rats were observed under light microscope. Results The expression of beta-endorphin in the hypothalamus of the rats was significantly higher in the PRF group than that in sham PRF group （P〈0.01） at 7, 14 d after PRF treatment. The expression of beta-endorphin was significantly higher in PRF 720 s group and PRF 480 s group than that in PRF 120 s group at 14 d after PRF treatment （P〈0.05）, which was higher in PRF 720 s group than that in PRF 480 s group, higher in PRF 480 s group than that in PRF 120 s group at 21 d after PRF treatment （P〈0.05）. The sciatic nerve structure changed slightly after PRF treatment, and showed a trend of recovery over time under light microscope. Conclusion The content of beta-endorphin in hypothalamus of CCI rats is significantly increased after PRF treatment with 120 s, 480 s and 720 s. Appropriately increasing the time of pulsed radiofrequency will maintain high concentration of beta-endorphin in hypothalamus of CCI rats for a long time, and may prolong the time of PRF analgesia.