The purpose of this study was to ascertain the role of the peripheral sympathetic activity on acupuncture analgesia. 50 rats which had a comparatively stable pain threshold and a more than 50% rise of pain threshold at 10 minutes after acupuncture induction were randomly divided into three groups: 1) 30mg/kg 6-OHDA + acupuncture; 2) 100mg/kg + acupuncture; 3) Saline + acupucturel All of them

6-OHDA and same volume of saline were administered intraperitoneally 5 days before experiment respectively. "Zusanli" and "pishu" points were electroacupunctured with 20 CPS

2-4 mA and 60 CPS 1-2 mA respectively. The analgesia effect of electro-acupuncture was estimated by using the potassium iontophoresis tail-flick test. The content of noradrenalin (NA) in brain and the change of fluorescent intensity of NA in the peripheral sympathetic nerve terminals were determined immediately after analgesia experiment. Results were summarized as follows: In 6-OHDA groups

the fluorescent intensity of NA in the peripheral sympathetic nerve terminals in organs such as gastric wall

duodenum

heart

kidney was markedly weaker than that in saline group. But the content of NA in cortex

diencephalon and brain stem was no significantly different. It suggested that only was the majority of the peripheral sympathetic nerve terminals damaged by inject- ing 6-OHDA

under this condition

the acupuncture analgesia was notably enhanced (1.15±0.047mA - 1.46±0.088 mA

p<0.01

n=12)

but in saline contral group

it was no change (1.28±0.073 mA - 1.23±0.093mA

p>0.05

n=23). The results suggested that besides central mechanism of acupuncture ana- lgesia

the excitability of the peripheral sympathetic system might be an important fact in acupuncture analgesia. In our previous studies

it had been found that acupuncture analgesia was almost simultaneous with the inhibitory effect of acupuncture on the peripheral sympathetic nerve

It is assumed that acupuncture inhibits the vasocontrction fibers of sympathetic nerve which in turn influence micrci- rculation. to change the excitability of free nerve endings

Moreover

the inhibitory effect of acupuncture on sympathetic nerve could decrease 5-HT releasing into blood from APUD cells

It might improve microcirculation and benefit the analgesia.