Objective: To observe the effect of intracerebroventricular(icv) injection of Sincalide(CCK-8) on the electroacupuncture(EA) analgesia by using discharges of neurons of Caudate nucleus(Cd) and radiant heat irradiation induced tail-flick reflex as the indexes.Methods: Eighty-six Wistar rats anesthetized by 20% urethane((1.0 g/kg)) were randomized into control

EA and EA+CCK-8 groups.Extracellular discharges of pain-excited neurons(PEN) and pain-inhibitory neurons(PIN) in Cd were recorded by using glass micropipettes(0.5-(1.0 μm) in diameter

10-(30 mΩ) in resistance).Radiant heat irradiation induced tail-flick latency (TFL) was used as the pain threshold index.EA((6 V)

(15 Hz) and continuous electric pulses) was applied to bilateral "Zusanli"(ST 36) for(15 min).Fifteen minutes after EA stimulation

CCK-8((10 ng)/(10 μL)) was injected slowly into the lateral cerebral ventricle(A:(-0.2 mm);R:(1.5 mm);H:(3.0 mm)) in a duration of(2 min).Results: 1) A total of 105 neurons including 63 PEN and 42 PIN were recorded in Cd.The radiant heat induced TFL simultaneously caused an increase in the discharge of PEN or a reduction in that of PIN

showing a painful effect of radiant heat on both the rat's behavior and central neuronal activity.2) EA at bilateral "Zusanli"(ST 36) 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

exhibiting an analgesic effect of EA.3) The analgesic effect of EA on PEN or PIN and TFL were simultaneously antagonized by icv injection of CCK-8((10 ng)/(10 μL)).Conclusion: The antagonism of CCK-8 to analgesic effect of EA shows the coordinative and consistent actions on the levels of discharges of central pain-related neurons and the whole behavior reflex.It suggests that reducing concentration of CCK-8 in the brain can potentiate the analgesic effect of clinical acupuncture

and the electrical activities of PEN and PIN being as the indexes of pain and analgesia are indeed feasible.