用奴佛卡因阻滞细纤维对电针镇痛作用的影响

一、用0.2%的奴佛卡因溶液作用于兔的腓神经,并限制受药物作用的神经长度在2毫米左右,可在一定时间内选择性阻断ⅢⅣ类纤维,而绝大部分ⅠⅡ类纤维仍保持传导功能。二、在奴佛卡因阻滞前,电针兴奋腓神经中全部ⅠⅡⅢⅣ类纤维,可使反射性下颌运动的幅度抑制91.7%;在阻断ⅢⅣ类纤维后,同样强度的电针仅使下颌运动幅度抑制29.3%,抑制作用持续的时间也缩短。因此认为细纤维的镇痛作用大于粗纤维的镇痛作用,在细纤维和粗纤维同时被兴奋的情况下,细纤维在镇痛信号的传入中起主要作用。

Influence of the Selective Block of Small Afferent Fibres by Novocaine on the Analgesic Effect of Electro-acupuncture

In this work, the different roles small and large afferent fibres play in the analgesic effect of electro-acupuncture have been analysed byusing the method of selectively blocking the small fibres of the peripheralnerve with novocaine. The reflexive jaw movement caused by the electricstimulation of peroneal nerve in wakened rabbits was taken as pain response,while stimulation of the same nerve with continuous rectangular impulses ata frequency of 5 cps was employed to imitate the electro-acupuncture atthe points. Results were as follows: a) Before the blockage, exciting all fibres of Groups Ⅰ, Ⅱ, Ⅲ, andⅣ with electro--acupuncture was shown to cause the amplitude of the refle-xive jaw movement to reduce by 91.7% in five minutes after the starting ofelectro--acupuncture. b) On applying 0.2% novocaine solution to the peroneal nerve and limi-ting the length of the nerve under the anaesthetic action to about 2 mm, thefibres of Groups Ⅲ and Ⅳ tended to be blocked completely or almostcompletely, but e amplitude of action potentials of Groups Ⅰ and Ⅱ fibres was reduced only by 6.4%. c) After the fibres of Groups Ⅲ and Ⅳ were blocked, however, elec-tro-acupuncture of the same intensity decreased the amplitude of the refle-xive jaw movement only by 29. 3%, thus indicating that the analgesic effectof electro-aoupuncture was largely inhibited by this block. Meanwhile, theduration of the analgesic effect was shown to be shortened as well. It was thus concluded that the analgesic action of the small afferentfibres is greater than that of the large ones.