Objective To study the simultaneous antagonism of cholecystokinin octapeptide (CCK-8) to the effects of electroacupuncture (EA) on the discharges of pain-related neurons in caudate nucleus (Cd) and the painful threshold measured by tail-flick latency (TFL) in rats. Methods The electrical changes of pain-excited neurons (PEN) or paininhibited neurons (PIN) in Cd and TFL which caused by radiant heat focused on the tail of rats were recorded simultaneously. Results ( 1 ) The radiant heat focused on the tail of the rat simultaneously caused an increase in the evoked discharge of PEN or a reduction in the evoked discharge of PIN and the tail-flick reflex, showing the painful effect of radiant heat. (2) EA at bilateral "Zusanli" for 15 min resulted in an inhibition of the electrical activity of PEN as well as a potentiation of the electrical activity of PIN and a prolongation of TFL, i.e. exhibiting the analgesic effect of EA. (3) The analgesic effect of EA on PEN or PIN and TFL were simultaneously antagonized by intracebroventricular (icv) injection of CCK-8 (10 ng/ 10μl). Conclusion The antagonism of CCK-8 to analgesic effect of EA shows the coordinative and consistent activities on the levels of the electrical activities of central pain-related neurons and the whole behaviour reflex.It suggests that the electrical activity of PEN and PIN as the markers of pain and analgesia are indeed feasible.