辣椒素局部用药对初级传入神经和P物质的影响

Effects of local administration of capsaicin on primary afferent nerve and substance P

目的：观察辣椒素眶下神经干局部给药对大鼠初级传入神经和P物质的影响，探讨其对三叉神经痛的潜在治疗意义。方法：2％辣椒素溶液直接于大鼠一侧眶下神经干给药，对侧做自身对照，分别在给药后3d及1、2、3、4、5、6周电镜观察双侧眶下神经纤维的变化，免疫组化方法检测三叉神经脊束尾侧核区（CNV）P 物质（SP）阳性颗粒的灰度值。结果：辣椒素给药后无髓神经纤维变性溶解，而有髓神经纤维完好；给辣椒素后CNV区SP免疫阳性颗粒灰度值明显高于对照侧（P ＜0．01），即SP含量明显降低，不同时间组之间SP含量没有明显差异。结论：辣椒素局部神经干给药能选择性毁损初级传入神经中的无髓纤维，减少CNV区SP含量，提示辣椒素局部给药对治疗三叉神经痛有临床意义。

Objective: To study the effects of capsaicin applied locally to infraorbital nerve on primary afferent nerve inadult rats. Methods:Capsaicin solution (2% ) was directly applied onto one lateral intraorbital nerve, and the contralateralnerve was used as self-control. Both experimental and control infraorbita1 nerves were observed under electron tnicroscope on3, 7, 14, 21, 28, 35 or 42 d after local administration. Substance P(SP)--like immunoreactive positive granules in both lateralnucleus caudalis spinalis nervi trigemini (CNV) were examined by immunohistochemical method. Results: Degenerated un-myelinated fibers in capsaicin-treated nerves were found under electron microscope, and no myelinated fibers changes werefound. The gray scale value of SP-like immunoreactive positive granules in the experimental side was markedly lower thanthat in the control side (P＜0. 01), while no significant difference was observed between different time groups. Conclusion:Local administration of capsaicin can produce selective destruction of unmyelinated fibers in primary afferent nerves, and canreduce the levels of SP in regions of CNV. The results suggest that local administration of capsaicin has potential therapeuticvalue for trigeminal neuralgia.