A review of recent approaches regarding the effect of peripheral serot- onin in acupuncture analgesia is what this article attempts to present. It has been reported in most data that acupuncture might have the effects of elevation of the platelet 5-HT content and depression of free 5- HT concetration in plasma

the latter being considered as a pain-producing agent. Besides

the increase of tryptophan in blood was also reported after acupuncture. It is well known that tryptophan

the precursor of 2-HT

can permeate into brain via blood-drain barrier and facilitate intracephalic sy- nthesis of 5-HT which is an analgesic transmitter in the brain. As for the activity of APUD cells after acupuncture

there were conflicting reports of augmentation or depression in release of serotonin from APUD cells. Moreover

an increase of mono-amine oxidase activity in platelets was de- monstrated afer acupuncture and was positively correlated with the efficacy of analgesia. However

the mechanism of that remains to be elucidated.