辣椒素阻断腓总神经C纤维的效应及其对电针“足三里”镇痛作用的影响

采用选择性阻断无髓C纤维的神经毒辣椒素（Cap）施于支配“足三里”的大鼠腓总神经干上,观察到1％Cap可使C复合动作电位明显减小,于给药后0、5、15、30和45分钟时分别为给药前C波波幅的68．3％。59．3％、56．9％。56．80和55．4％,差异均非常显著（P＜0．001,n＝9）。但C波并未完全消失。1．5％Cap对C纤维的阻断效应于5分时较强为46．3％,15和30分时分别为54．5％和53％,与1％Cap的接近。延长1．5％Cap作用时间到24小时后,6例实验中4例C波减小,2例完全消失。在Cap处理前,电针“足三里”有明显的镇痛作用,于针后0、15、20和30分对中缝大核（NRM）神经元的伤害性反应有明显的抑制作用（P＜0．05,n＝7）。但在1．5％Cap作用腓总神经30分C波被部分阻断的情况下,电针“足三里”虽仍能使痛反应减小,但镇痛效应已大大削弱,无统计学意义。在一例腓总神经的C波几乎完全消失的情况下,电针该侧“足三里”对痛反应已无明显的抑制作用,但电针对侧“足三里”仍有明显的镇痛效应。结果表明传入C纤维在穴位针刺引起镇痛效应中起重要作用,绝非可有可无。

The Effects of Capsaicin Blocking C Fibers of Nervi Peroneus Communis and Its Influence on Analgesia of EA at "Zusanli

The aim of the. work was to study the effects of capsaicin (Cap) blocking afferent C fibers of n.peroneus communis innervating "Zusanli" and the influence of Cap on analgesia produced by elec-troacupuncture (EA) at "Zusanli".The highest antidromic C waves of n. peroneus communis in rats were recorded. 1 % ~ 1. 5% capsaicin soi 25μl were topically applied on the nerve between the electrodes of stimulation and record,and the changes of C wave amplitude were analysed.After 1 % Cap was applied to the nerve, the C waves were immediately reduced to 68. 3 % of con-trol before Cap treatment and kept at 55. 4 % for 45 minutes (P < 0. 001, n =9), having not been re-covered but they were not yet completely blocked. The vehicle (10% Tween80 liquid paraffin) applied on the nerve have not the effects on C waves (n = 7).Then the dose of capsaicin was increased to 1. 5 % Cap sol 25μl, after it was applied on the nerve trunk, the C waves were decreased immediately to 77. 7% of control, then the C wave amplitudes were decreased to 46. 2 % (P < 0.01 ) in 5 minutes, then maintained at 54. 5 % ~ 53. 3 % for 15 ~ 30 minutes (P < 0. 05) (n = 4). But the C waves were not yet completely blocked.When the action time of 1. 5 % capsaicin sol was prolonged for 24 hours, the C waves were de-creased in 4/6 experimental examples, and they were completely blocked only another 2 examples.The analgesia of electroacupuncture (EA) at "Zusanli" before and after 1. 5 % Cap applying on the nervi peroneus communis for 30 minutes was observed. Before Cap treatment, EA at "Zusanli" could obviously inhibit the nociceptive responses of NRM neuron induced by stimulation of rats tail tip in 0 10. 15 .20 and 30 minutes (P < 0. 05, n = 7). But after Cap, the inhibition of EA at "Zusanli" .on the nociceptive responses was clearly weakened(P >0. 05, n = 7 ). In a case (NO. 88107 ), that C wave was nearly completely b1ocked, analgesia of EA at the lateral "Zusanli" disappeared, but EA at con-tralateral "Zusanli" could still produce analgesia.It is shggested .that role of afferent C fibers in EA analgesia is very important and itidispensable,