In the present investigation the intensity of stimulated electro-acupuncture (EA) was measured by electrophysiological collision technique. In the behavioral experiments

by applying the weak electro-acupuncture pulses (50 Hz

1

1

. 5mA)

not enough to activated Aδ afferent fibers

to Yanglingquan and Xuanzhong points

the latency of nociceptive hind limb withdrawal reflex

but not tail -flick latency was prolonged. Administered intraperitoneally

both theophylline and caffeine

P1purinergic (adenosine) receptor antagonists

could block the electroacupuncture-induced elevation of the nociceptive thresholds in a dose-effect related manner

whereas dipyridamole

an inhibitor of adenosine release

could shorten the after effect of electro-acupuncture in a dose dependent way.These results suggest that weak electro-acupuncture may induce analgesia and purines appear to be involved in this process