Objective To observe the effect of electroacupuncture(EA) and moxibustion-like thermal stimulation with different temperatures at "Zusanli"(ST 36) on pain reactions in transient receptor potential vanilloid type 1 knock-out(TRPV 1-/-) mice so as to study its mechanisms underlying analgesia.Methods Ten C 57 BL/6 mice and 10 TRPV 1-/-mice were respectively divided into control and TRPV 1-/-groups.EA(0.3 mA

1.0 mA

3.0 mA) or thermal water-bath(38 ℃

43 ℃

46 ℃) stimulation was applied to the right ST 36 for 20 min and 10 min

respectively.Mechanical and thermal pain thresholds of the bila-teral paws were detected before and immediately after stimulation

and 5 min after EA stimulation at 0.3 mA

3.0 mA and thermal water-bath stimulation at 38 ℃

46 ℃

separately.Results ① The thermal threshold was significantly higher in TRPV 1-/-mice than in C 57 BL/6 mice(P<0.001).② In C 57 BL/6 mice

both homolateral and contralateral mechanical and thermal pain thresholds were significantly increased following 1.0 mA

3.0 mA EA

and 43 ℃ and 46 ℃ thermal stimulation of the right Zusanli(ST 36)(P<0.05

P<0.01

P<0.001);while only homolateral mechanical and thermal pain thresholds were increased after 0.3 mA EA and 38 ℃ thermal stimulation of ST 36(P<0.05

P<0.01).In TRPV 1-/-mice group

both homolate-ral and contralateral mechanical and thermal pain thresholds were significantly increased by 3.0 mA EA stimulation of ST 36(P<0.05

P<0.01).Bilateral mechanical thresholds and homolateral thermal threshold were significantly increased by 1.0 mA EA stimulation of ST 36(P<0.05

P<0.01)

while only homolateral mechanical and thermal pain thresholds were increased by 0.3 mA EA

and 43 ℃ and 46 ℃ thermal stimulation(P<0.05

P<0.01).Additionally

only the homolateral mechanical threshold was increased by 38 ℃ thermal stimulation(P<0.05).③ The mechanical and thermal pain thresholds of the bilateral limbs were increased to some extent in TRPV 1-/-mice compared with those of C 57 BL/6 mice following EA and thermal stimulation of the right ST 36.④ Five minutes after 0.3 mA

3.0 mA EA and 38 ℃

46 ℃ thermal water-bath stimulation

both mechanical and thermal pain thresholds recovered to their baseline levels in both TRPV 1-/-and C 57 BL/6 mice.Conclusion Both EA and thermal stimulation of the right ST 36 can raise mechanical and thermal pain thresholds in TRPV 1-/-and C 57 BL/6 mice

but needing a stronger stimulation in TRPV 1-/-mice

suggesting an involvement of TRPV 1 receptors in analgesia.