Objective: To better understand the function of mast cells in acupuncture points (acupoints) inacupuncture-induced analgesia. The author tested their sensitivity to mechanical, thermo and light stimulation.Methods: The tail flick model was applied to measure analgesia in rats, and the author determined the density of mast cells in tissue slices and their degranulation ratio before/after acupuncture. The author also applied the patch-clamp technique to investigate activation of human mast cells (HMC 1 cell line) by mechanical stress or noxious heat, and the author optically observed degranulation phenomena of mast cell in response to red laser light.Results: Manual stimulation by acupuncture at Zusanli (ST 36) of the rat resulted in analgesia and the effect was more pronounced than after stimulation of a sham point nearby the acupuncture point. A higher density of mast cells was found at Zusanli (ST 36) than at the sham point, and acupuncture caused a remarkable increase in degranulation. Pretreatment with disodinm chromoglycate (DSCG, a mast cell stabilizer) injected into Zusanli (ST 36) impaired the analgesic effect of acupuncture. In whole-cell patch-clamp, increasing hydrostatic pressure induced a current that could be inhibited by 10 ～tM of ruthenium red (RuR), an inhibitor of TRPV2. Temperatures above 50～C, which are reached during moxibustion, induced a similar RuR-sensitive current. Laser light of 640 nm (48 mW) applied to acupoints had been shown previously to be highly effective in analgesia. 20 min of light application induced pronounced degranulation in HMC 1 that could be blocked by 0.02 g/mL DSCG as well as by RuR. Conclusion: The author found that mechanical stimulation of acupoints is associated with mast cell degranulation and mast-cell degranulation can be correlated with acupuncture-induced analgesia. The author suggest that TRPV2 plays a key role in mast-ceU degranulation in response to mechanical, thermal (moxibustion) as well as laser-light stimulation forming a facilitating step in acupuncture-induced analgesia.