Objectives

To investigate the analgesic effect of high-voltage pulsed radiofrequency (HV-PRF) on the dorsal root ganglion (DRG) for neuropathic pain induced by spared nerve injury (SNI) in rats, especially the influence of this treatment on the DRG ultrastructure and voltage-gated sodium channel 1.7 (Nav1.7) level in the DRG.

Materials and Methods

One hundred fifty adult male Sprague-Dawley rats were randomly divided into five groups: Sham, SNI, Free-PRF, standard-voltage PRF (SV-PRF), and HV-PRF. The 45V-PRF and 85V-PRF procedures applied to the left L5 DRG were performed in SV-PRF group and the HV-PRF group, respectively, on day 7 after SNI, whereas no PRF was concurrently delivered in Free-PRF group. The paw mechanical withdrawal threshold (PMWT) was detected before SNI (baseline) and on days 1, 3, 7, 8, 10, 14, and 21. The changes of left L5 DRG ultrastructure were analyzed with transmission electron microscopy on days 14 and 21. The expression levels of Nav1.7 in left L5 DRG were detected by immunofluorescence and Western blot.

Results

Compared with the Free-PRF group, PMWT in the SV-PRF group and HV-PRF group were both significantly increased after PRF (all p < 0.05). Meanwhile, the PMWT was significantly higher in the HV-PRF group than that in the SV-PRF group on days 14 and 21 (all p < 0.05). There were statistically significant differences between the SV-PRF and Free-PRF groups (p < 0.05). Similarly, statistically significant difference was found between the HV-PRF and Free-PRF groups (p < 0.05). Especially, comparison of the SV-PRF group and the HV-PRF group revealed statistically significant difference (p < 0.05). The Nav1.7 levels were significantly downregulated in the SV-PRF group and HV-PRF groups compared to that in the Free-PRF group (all p < 0.01). A significantly lower Nav1.7 level was also found in the HV-PRF group compared to that in the SV-PRF group (p < 0.05).

Conclusions

The HV-PRF produces a better analgesic effect than SV-PRF applied to the DRG in SNI rats. The underlying mechanisms may be associated with improving the histopathological prognosis and the downregulation of Nav1.7 levels in the DRG.

中文翻译：

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高压脉冲射频对留置神经损伤大鼠背根神经节超微结构及Nav1.7水平的影响

目标

探讨高压脉冲射频（HV-PRF）对大鼠背根神经节（DRG）的镇痛作用，特别是该治疗对大鼠背根神经节超微结构和电压的影响。 DRG 中的门控钠通道 1.7 (Nav1.7) 水平。

材料和方法

150 只成年雄性 Sprague-Dawley 大鼠随机分为 5 组：Sham、SNI、Free-PRF、标准电压 PRF (SV-PRF) 和 HV-PRF。SV-PRF 组和 HV-PRF 组分别在 SNI 后第 7 天对左侧 L5 DRG 实施 45V-PRF 和 85V-PRF 程序，而在 Free-PRF 组中没有同时递送 PRF。在 SNI（基线）前和第 1、3、7、8、10、14 和 21 天检测爪机械缩回阈值（PMWT）。在第 14 天和第 14 天用透射电子显微镜分析左侧 L5 DRG 超微结构的变化， 21.免疫荧光和Western blot检测左L5 DRG中Nav1.7的表达水平。

结果

与Free-PRF组相比，SV-PRF组和HV-PRF组的PMWT在PRF后均显着增加（均p  < 0.05）。同时，在第 14 天和第 21 天，HV-PRF 组的 PMWT 显着高于 SV-PRF 组（均p  < 0.05）。SV-PRF 组与 Free-PRF 组比较差异有统计学意义（p  < 0.05）。同样，HV-PRF 组和 Free-PRF 组之间存在统计学差异（p  < 0.05）。特别是 SV-PRF 组和 HV-PRF 组的比较显示出统计学上显着的差异 ( p < 0.05)。与 Free-PRF 组相比，SV-PRF 组和 HV-PRF 组的 Nav1.7 水平显着下调（均p  < 0.01）。与 SV-PRF 组相比，HV-PRF 组的 Nav1.7 水平也显着降低（p  < 0.05）。

结论

与应用于 SNI 大鼠背根神经节的 SV-PRF 相比，HV-PRF 产生更好的镇痛效果。潜在机制可能与改善组织病理学预后和 DRG 中 Nav1.7 水平的下调有关。