The experiment was to study whether the effects of electroacupuncture (EA)on neurons in nucleus raphe magnus (NRM)were influenced after lesion of bila- teral pyramidal tracts (PT) in the rats.unit discharges of NRM were recordedextracellularly with glass microelectrodes

and their nociceptive responses wereinduced by train electro-stimulation of tail.It was researched only the neuronswith excitory response to noxious stimulation of the tail.1.The effects of bilateral ‘Zusanli’ acupoint on 31 NRM neurons wereobserved in control group.EA had a tendency to activate NRM neurons

butinhibited obviosly nociceptive response of the neurons at 0-30 minutes (P<0.01).The effects of EA of PT control group (PT exposed and kept intact) wererecorded on 8 units in NRM.EA had a tendency to activate the neurons

butinhibited obviously nociceptive response of the neurons and decreased nocice-ptive response rate 25.3±8.7% at o minte (n=8

P<0.05)3.EA after the PT lesion

it obviously inhibited nociceptive response ofthe neurons in NRM at 0-20 minutes (n=9

P<0.01-0.05).It inhibited noci-ceptive ressponse of all the neurons and decreased noeiceptive response rate57.8±11.6% at o minute (P<0.01).The effect was larger than the effect ofEA of PT control group and increased 32.5% at o minute (P<0.05) than this.It also increased the effect of EA activating the neurons than PT control group.The results suggest that SM may influence th effect of EA analgesia

whichinvolves in both PT and extrapyramidal system (EPS).The PT may decreasethe effect of EA

but the EPS may increase the effect of EA.