C纤维不是电针镇痛的主要传入纤维,而是弥散性伤害性抑制控制的主要纤维

C FIBER IS NOT NECESSARY IN ELECTROACUPUNCTURE ANALGESIA,BUT NECESSARY IN DIFFUSE NOXIOUS INHIBITORY CONTROLS(DNIC)

电针刺激通过何种纤维传入中枢产生镇痛作用,至今仍有争论。范少光等采用我室常用电针参数,以大鼠行为反应为指标,观察到电针(Electroacupuncture,EA)镇痛信息主要不是由 C 纤维传入。本工作用辣椒素选择性阻断 C 纤维传导后,观察了 EA 和伤害性热刺激(Noxious heat,NH)对脊髓广动力范围(Wide DynamicRange,WDR)神经元抑制作用的影响,进一步对上述问题作探讨。

Experiments were carried on rats.We applied capsaicin topically on sciatic nerve and used the techniques of extracellular recording and nerve trunk recording. Our results showed that the size of C compound action potentials in nerve trunk and C fiber response of spinal cord WDR neurons were decreased by at least 70% (mean)after topical application of capsaicin (250μg)on the nerve, but A compound action potentials and A fiber response did not change signifi- cantly.It indicated that capsaicin blocked C fiber conduction selectively. Electroacupuncture (EA:100 Hz,0.1ms,3V)applied on left Zusanli (S36) and Sanyinjiao (Sp6)points inhibited C fiber response of spinal WDR neurons in the right side.The effect was similar to animal behavior analgesia elicited by EA.After applying capsaicin (250μg)topically on left sciatic nerve,the inhibitory effect of EA on WDR neurons remained essentially intact (from 61.3±12.0% to 59.0±11.6%,n=6,P>0.05).It indicated that C fiber was not important in EA analgesia. Noxious heat (NH)applied on left hind paw by immersing the hind paw into 52℃ water inhibited C fiber response of spinal WDR neurons in the right ide.It was called diffuse noxious inhibitory controls (DNIC).After applying capsaicin (250μg)topically on left sciatic nerve,the inhibitory effect of NH on WDR neurons was dramatically decreased (from 77.7±8.5% to 8.1±8.9%, n=6,P<0.001).It indicated that C fiber was important in DNIC. Both inhibitory effects of NH and EA were not changed by vehicle tre- atment. EA is different from DNIC,at least in afferent fiber.