Objective: To investigate the role of mast cells in acupuncture analgesia in rats.Methods: A total of 48 Sprague Dawley(SD) rats were divided into normal control

acupoint [("Zusanli"(ST 36)]-acupuncture(Acu)

non-acupoint(3 mm left to ST36)

disodium cromoglycate(DSC

0.02 g/mL

for acupoint injection)

normal saline(NS

for acupoint injection)

DSC+Acu

NS+Acu and DSC+contralateral Acu groups

with 6 cases in each group.The latency of tail flick response to heat irradiation was used as the pain threshold."Zusanli"(ST 36) was punctured with filiform needle and stimulated by lifting and thrusting the needle for 30 min.After sacrifice under anesthesia(1% embutal)

tissues of ST36 area were sampled

sliced(4 μm)

and stained with Toluidine Blue for skin and Neutral Red for muscles.Results: Compared with normal control group

the ratios of pain threshold increased significantly in all the 7 experimental groups(P<0.05)

and those of DSC and NS groups were significantly lower than those of acupoint-Acu

non-acupoint

DSC+Acu

NS+Acu and DSC +contralateral Acu groups(P<0.05).Compared with DSC+Acu group

the ratios of NS+Acu and DSC+contralateral Acu groups were evidently higher(P<0.05

0.01).Compared with control group

the degranulation ratio of acupoint-Acu group was significantly higher(P<0.05

0.001 in muscle and skin separately)

and the ratio of DSC+Acu group was markedly lower than that of acupoint-Acu group(P<0.01 in skin).Conclusion: Acupuncture of ST36 has a significant analgesia and enhances the degranulation of mast apparently cells

which is weakened by injection of DSC in the acupoint area

suggesting an important role of mast cells in acupuncture-induced analgesia.