Objective To investigate the relationship between acupoint sensitization on the body surface and neuronal intrinsic excitability of the medium-and small-size dorsal root ganglion(DRG) neurons from the perspective of ion channel kinetics in mice with gastric ulcer. Methods Male C57BL/6J mice were randomly divided into control(n=32) and model groups(n=34). The gastric ulcer model was established by injection of 60% glacial acetic acid(0.2 mL/100 g) into the gastric wall muscle layer and submucosa near the pylorus in the minor curvature of the stomach. In contrast

the same dose of normal saline was injected in the same way in the control group. Six days after modeling

Evans blue(EB) solution was injected into the mouse's tail vein for observing the number and distribution of the exudation blue spots on the body surface. Histopathological changes of the gastric tissue were observed by H.E. staining. Then

whole-cell membrane currents and intrinsic excitability of medium-and small-size neurons in the spinal T9-T11 DRGs were measured by in vitro electrophysiology combining with biocytin-ABC method. Results In the control group

EB exudation blue spots were not obvious

while in the model group

the blue spots on the body surface were densely distributed in the area of spinal T9-T11 segments

the epigastric region

and the skin around “Zhongwan”(CV12) and “Huaroumen”(ST24) regions

and near the surgical incision region. Compared with the control group

the model group had a high level of eosinophilic infiltrates in the submucosa of gastric tissues

severe gastric fossa structure damage

gastric fundus gland dilation and other pathological manifestations. The number of exudation blue spots was proportional to the degree of inflammatory reaction in the stomach. In comparison with the control group

the spike discharges of type II of medium-size DRG neurons in T9-T11 segments were decreased

and the current of whole-cell membrane was increased

basic intensity was decreased(P<0.05)

discharge frequency and discharge number were increased(P<0.01

P<0.000 1); while the discharges of type I small-size DRG neurons were decreased

those of type II neurons increased

the whole-cell membrane current was decreased

and discharge frequency and discharge number were decreased(P<0.01

P<0.000 1). Conclusion Both the medium-and small-size DRG neurons from the spinal T9-T11 segments involve in gastric ulcer-induced acupoint sensitization via their different spike discharge activities. And intrinsic excitability of these DRG neurons can not only dynamically encode the plasticity of acupoint sensitization

but also can help us understand the neural mechanism of acupoint sensitization induced by visceral injury.