The aim of this paper is to investigate the corticofugal modulation of nucleus periaqueductal gray(PAG) after electroacupuncture by topical administration of GABA on frontal cortex. Experiments were carried out on restrained rabbits immobilized with gallamine. Electrial stimulation of the n. suralis was used as the noxious stimulation. Single unit activites of PAG neurons were record with glass microelectrodes extracellularly."Zusanli" and"Huantiao" points were stimulated by the electroacupuncture bilaterally. GABA was applied topically by means of 3×3mm

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filter paper and placed on the frontal cortex. It was shown that the responses of most PAG neurons evoked by noxious stimulation were inhibited after simple electroacupuncture. On the contrary

the acupuncture effect on PAG neurons was abolished when GABA was administed on frontal cortex. However

the effect of saline control resembled that of simple acupuncture. This result suggested that the corticofugal modulation from frontal cortex may play a role in acupuncture analgesia.