Effect of changing the functional state of frontal cortex by GABA on the acupuncture effect of PAG neurons

: 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. Electrical stimulation of the n. suralis was used as the noxious stimulation. Single unit activities 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 x 3 mm2 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 administered 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.