[Role of afferent C fibers in electroacupuncture of "zusanli" point in activating nucleus raphe magnus].

The purpose of the present work is to study whether the analgesia of“Zusanli”EA was mainly produced by its noxious effect.The antidromic C waves on N.peroneus communis innervating the area of“Zusanli”point were recorded.When“Zusanli”point was stimulated by trains of stimuli,the amplitude of theantidromic C wave was obviously decreased due to collision with the orthodromicstimulation.It was suggested that EA of“Zusanli”could excite some C fibers.It was observed that when the stimulation intensity reached the threshold of C fiber,the NRM neurons were obviously activated,and when it reached or exceeded theintensity for producing the maximal C wave,the NRM neurons were highly acti-vated.Therefore,EA analgesia is probably produced mainly by its noxious stimu-lus component,especially carried by C fibers,via a negative feedback mechanismin modulating pain.