In recent years using cortical evoked potentials(CEP)as an indexmany researchers have studied the role of the cerebral cortex in acupunct-ure analgesia.However

reports on identifying the characteristics of CEPhave been scarcely found.Thus

there are still some contradictory opinionsabout whether or not CEP can be justly used as an index to reflect painfulsensation and whether or not the cerebral cortex is involved in the mechan-ism of acupuncture analgesia.The primary intent of this work is toidentify the relatioship between CEP and pain

and to further explore therole of the cerebral cortex in acupuncture analgesia by analizing the corticalpotentials evoked by noxious stimulation and observing the effect of electro-acupuncture on them.The experiments were carried out on 42 cats.The animals were cons-cious

but immobilized during the process of experiments.The right peronealnerve was electrically stimulated.The compound action potentials of thenerve and the CEP on the contralateral somatosensory area were simul-taneously recorded.Both of them were fed to a computer to be averagedthrough different channels via individual amplifiers.The points “Zusan Zusanli”and “Huantiao” on the right side were stimulated by electroacupuncture.The results were as follows:1.The pat erns of compound action potentials and corresponding corticalpotentials elicited by electrical stimuli with various intensities were differ-ent.The electrical stimulation with the intensities sufficient to activate Aδfibers caused significant increaing the amplitudes of the late components P2and N2(with mean latency of 49.4 ms and 117.5 ms respectively)of CEP.2.In 10 cats following an intravenous injection of ketamine(20mg/kg)the amplitude of each component of the cortical potentials induced by nox-ious stimuli With the intensities strong enough to excite Aδ and C fibers was reduced to various extent.The diminution of the amplitudes of P2 andN2 was of significance.3.Administering morphine(6-8mg/kg)intravenously resulted in remark-able inhibiton of the late components P2 and N2 of cortical potentialselicited by noxious stimulation in 10 cats.In the control experiments withequal volume of saline solution the CEP showed no considerable changes.4.Electroacupuncture at points“zusanli” and “Huantiao”obviously depressed the amplitudes of both late components and early ones of CEP in 11cats.It is established that the late components P2 and N2 of cortical po-tentials evoked by noxious stimulation are closely related to pain

and theCEP is inhibited by electroacupuncture.The present data are consistentwith our previous findings in human subjects.Therefore

it is suggestedthat CEP can be used as one of the nonspecific indexes reflecting painfulsensation.Thus

we further consider that the cerebral cortex does play arole in the mechanism of acupuncture analgesia.