Effects Of Electroacupuncture And Regional Thermal Stimulation At "Zusanli"(ST36) On Pain Threshold Of TRPV1and ASIC3Knock-out Mice

Objective: To observe the effect of electroacupuncture (EA) and moxibustion-likethermal stimulation with different temperatures at Zusanli (ST36) on pain threshold in acidsensing ion channel3knock-out (ASIC3-/-) and transient receptor potential vanilloid type1knock-out (TRPV1-/-) mice so as to study its underlying mechanisms in relieving pain.Methods:10C57BL/6mice,10TRPV1-/-mice and10ASIC3-/-mice wererespectively divided into control and groups. EA (0.3mA,1.0mA，3.0mA) or thermalwater-bath (38℃,43℃46℃) stimulation was applied to the right ST36(right side) for20min and10min, respectively. Mechanical and thermal pain thresholds of the bilateral pawswere detected before stimulation, and immediately and5min after EA stimulation at0.3mA,1.0mA,3.0mA and thermal water-bath stimulation at38℃,43℃and46℃,separately.Results:①Compared with C57BL/6mice, the thermal threshold was significantlyhigher in TRPV1-/-mice (P<0.001), while the mechanical threshold was significantlyhigher in ASIC3-/-mice (P<0.001).②In C57BL/6mice, both homolateral and contralateralmechanical and thermal pain thresholds were significantly increased following1mA-,3mA-EA, and43℃and46℃thermal stimulation of the right Zusanli(ST36)(P<0.05，P<0.01，P<0.001)；while only homolateral mechanical and thermal pain thresholds wereincreased after0.3mA EA and38℃thermal stimulation of ST36(P<0.05，P<0.01). InTRPV1-/-mice group, both homolateral and contralateral mechanical and thermal painthresholds were significantly increased by3.0mA EA stimulation of ST36(P<0.05， P<0.01). The homolateral mechanical and thermal pain thresholds were significantlyincreased by0.3mA-,1mA-EA, and46℃thermal stimulation (P<0.05，P<0.01, P<0.001).Only the homolateral mechanical pain threshold was significantly increased by38℃thermal stimulation (P<0.05).43℃thermal stimulation has no obvious impact on painthreshold of the TRPV1-/-mice (P>0.05). In ASIC3-/-group, both homolateral andcontralateral mechanical and thermal pain thresholds were significantly increased by1mA-,3mA-EA,43℃and46℃thermal stimulation (P<0.05). Only the homolateralthermal pain threshold was significantly increased by38℃thermal stimulation(P<0.05).③The mechanical and thermal pain thresholds of the bilateral limbs weredecreased to some extent in TRPV1-/-mice and ASIC3-/-mice compared with those ofC57BL/6mice following EA and thermal stimulation of the right ST36.④Five minutesafter0.3mA-,1.0mA-,3.0mA-EA and38℃,43℃and46℃thermal water-bathstimulation, both mechanical and thermal pain thresholds recovered to their baseline levelsin three groups.Conclusion: Both EA and thermal stimulation of the right ST36can raise mechanicaland thermal pain thresholds in TRPV1-/-mice、ASIC3-/-mice and C57BL/6mice. BothTRPV1and ASIC3are involved in acupuncture and moxibustion analgesia.