In order to understand the role of cholinergic system in caudate nucleus during acupuncture analgesia

the microinjection technique Was used. 4μg of hemicholine-3 (HC-3) which inhibits biosynthesis of ACh was microinjected into caudate nucleus in 16 rabbits. There were no significant changes on the pain threshold and body temperature in the rabbits. But the effect of acupuncture analgesia was partially antagonized by HC-3. At the 30th minute of acupuncture the pain threshold was only increased by 0.42±0.08 mA from that before acupuncture

which differed significantly from the acupuncture control group (P<0.005). In addition

2μg of eserine was micro— injected into caudate nucleus in 11 rabbits

there was no significant change on the basic pain threshold

but when the microinjection of eserine was fo- llowed by electroacupuncture

the effect of acupuncture analgesia was mar- kedly increased

at the 27th minute of acupuncture the pain threshold incr- eased by 1.60±0.16 mA from that before acupuncture

which differed signi- ficantly from the acupuncture control group(P<0.02). According to our results

it may be suggested that cholinergic system in caudate nucleus plays an important role in acupuncture analgesia.