In this study we investigated that whether the corticofugal modulation fromSH is involved in the acupuncture effects on PAG. It was carried out on 32restrained adult cats. The unit activities of PAG were recorded by glass microelectrodes. Elect-rical stimulation on the right superficial peroneal nerve was taken as thenoxious stimulation. The results showed that electroacupuncture (EA) atHuantiao (G 30) and Yanglingquan (G 34) points could inhibited the nocice-ptive responses of PAG neurons

i.e

the changes of the firing rates inducedby the noxious stimulation were lessened 0-12.5 minusts after ceasing EA(n=15

P<0.01). When a piece of filter paper damped with 0.5M GABA was