实验性坐骨神经痛中辣椒素敏感初级传入纤维的作用

The role of capsaicin-sensitive primary afferents in experimental sciatic pain

目的通过局部破坏坐骨神经中辣椒素敏感传入纤维（CSPA），确定CSPA在自体椎间盘直接压迫L5神经根所诱导的机械刺激痛觉过敏的作用。方法取大鼠自体尾部椎间盘组织放置在L5神经根下，造成对L5神经根的直接压迫，建立椎间盘突出致坐骨神经疼痛动物模型。同时暴露大鼠左侧坐骨神经，给予辣椒素溶液或溶媒处理。术前及术后不同的时间点测量大鼠双侧后足底机械刺激疼痛阈值的变化。在3周当机械刺激疼痛阈值降到最低时，利用免疫组织化学染色方法，测定脊髓后角中c—fos蛋白空间表达变化。结果用辣椒素处理坐骨神经，完全阻止了椎间盘压迫神经根所诱致的机械刺激疼痛阈值的降低。椎间盘直接压迫L5神经根能够诱导后角中c—fos蛋白表达，而辣椒素处理坐骨神经能够抑制后角中c—fos蛋白的表达。结论主要终止于脊髓后角浅层的CSPA纤维，可能在新的坐骨神经疼痛动物模型机械刺激痛觉过敏的发生中起着关键作用。

Objectives To determine the effect of destroying capsaicin-sensitive primary afferents （CSPA） fibers on paw withdrawal mechanical threshold （PWMT） induced by the direct compression of L5 nerve root with autogolous disc. Methods The procedure used autologous disc of the rats from the coccygeal intervertebral discs to apply direct pressure to the L5 dorsal root. PWMT was measured at the different time points post-surgery and pre-surgery. The changes in spatial expression pattern of c-fos protein in the spinal cord were also determined at 3 weeks when PWMT decreased to the peak. Results The pretreatment with capsaicin produced a complete prevention of mechanical hyperalgesia induced by disc compression. The direct compression of L5 nerve root produced an obvious expression of los-like immunoreactivity neurons in the dorsal horn of the spinal cord, which was significantly decreased by pretreatment with capsaicin. Conclusions The study shows that CSPA fibers, which mainly terminated in superficial layers of dorsal horn, may play a key role in mechanical hyperalgesia in the new sciatica model.