The main purpose of the present paper is to investigate the influence of the ACh on the metabolism of 5-HT in the brain of rat during acupuncture analgesia(EA). The results find that;1)the pain threshold and the contents of ACh

5-HT and 5-HIAA in brain of rat were both significantly enhanced at simultaneously by EA.2)EA could further increase or decrease the contents of ACh

5-HT and HIAA in the brain of rats which had been treated by eserine or hemicholine (HC-3).The regression analysis indicate that the relationship correlation between the percentage of increase or decrease of ACh and 5-HT

5-HIAA in rat brain by eserine or HC-3 during EA present linear positive correlation. These results suggeste that ACh could influence the metablism of 5-HT under the action of EA.Thus it is considered that the role of ACh in EA is probably refered to its effect on the metabolism of 5-HT in certain extent