Objective To observe the effect of acupuncture of "Zusanli"(ST 36) on immune function in progressively exhausted swimming rats so as to reveal its mechanism underlying improvement of strenuous exercise.Methods Thirty-two SD rats were randomly allocated into control group

strenuous exercise(model) group

acupuncture-Xuehai(SP 10) group

Acupuncture-Zusanli(ST 36) group(n=8/group).The rats were forced to have a swimming in a water tank for 15-90 min in the first 8 days(once daily)

then

a progressively exhausted load swimming 1-3 times everyday from day 9 to 13.Bilateral SP 10 and ST 36 were punctured with filiform needles and stimulated with uniform reinforcing and reducing manipulation

once daily

after termination of the swimming and for 13 days.Serum interferon-gamma(IFN-γ) and interleukin-4(IL-4) contents were assayed by using enzyme linked immunosorbent assay.The rat's body weight and the spleen weight were weighted by using an electronic balance for calculating the spleen index(spleen weight /body weight ×100%) after killing the rat under deep anesthesia.Results Compared with the model group

the time of swimming-induced exhaustion appearing at the first time from day 9 to day 13 in the SP 10 and ST 36 groups was apparently lengthened(P<0.01).No significant difference was found between SP 10 and ST 36 groups in the time of swimming-induced exhaustion appearing at the first time of the forced swimming.Compared with the control group

the spleen index

serum IFN-γ contents and IFN-γ/IL-4 in the model group were decreased significantly(P<0.01

P<0.05).In comparison with the model group

the serum IL-4 contents in the SP 10 and ST 36 groups were decreased markedly(P<0.05

P<0.01)

and serum IFN-γ content and IFN-γ/IL-4 in the ST 36 group were increased significantly(P<0.05

P<0.01).The IFN-γ level was significantly higher in the ST 36 group than in the SP 10 group(P<0.05).No significant diffe-rences were found between SP 10 and ST 36 groups in the spleen index

IL-4 and IFN-γ/IL-4(P>0.05).Conclusion Acupuncture at "Zusanli"(ST 36) can lengthen the time of forced swimming-induced exhaustion

and upregulate serum IFN-γ content and IFN-γ/IL-4 in exhausted swimming rats

which may contribute to its effect in correcting Th 1/Th 2 imbalance after strenuous exercise.The effect of acupuncture of ST 36 is superior to that of acupuncture of SP 10.