Objective To discuss the effects of different intensity electroacupuncture（ EA） at different acupoints on visceral nociceptive pain response induced by colorectal distention（ CRD） and its possible mechanism. Methods A total of 54 Sprague-Dawley（ SD） rats were received electrophysiological experiments（ 30 rats） and morphological experiments（ 24 rats）. In electrophysiological experiments

6 rats were selected for CRD stimulation to induce the rectus abdominis myoelectricity threshold. The remaining rats were randomly divided into Zusanli（ ST36） group

Tianshu（ ST25） group and Quchi（ LI11） group

with 8 rats in each group. Under inhalation anesthesia with isoflurane

CRD stimulation was given to cause visceral injury pain. EA with current of 1 mA and 3 mA were used to stimulate rats’ "Zusanli"（ ST36）

"Tianshu"（ ST25）

and "Quchi"（ LI11）

for 140 s. The area

frequency

and amplitude of the curve of the rectus abdominis myoelectric activity were recorded. The rats for morphological experiments were randomly divided into normal group

model group

1 mA Zusanli（ ST36） group

1 mA Tianshu（ ST25） group

1 mA Quchi（ LI11） group

3 mA Zusanli（ ST36） group

3 mA Tianshu（ ST25） group and 3 mA Quchi（ LI11）group

with 3 rats in each group. EA stimulation last for 30 min. Immunohistochemical method was used to observe the effects of EA stimulation with different intensity at different acupoints on the expression of c-fos positive neurons in solitary tract nucleus. Results CRD of 60 mmHg could induce visceral pain of rats

which showed that the area

frequency and amplitude of the rectus abdominis myoelectric curve increased significantly

and the difference was statistically significant than before CRD stimulation（ P < 0. 01）

so it was selected as CRD stimulus value. 1 mA EA at"Tianshu"（ ST25） could significantly improve the release of rectus abdominis myoelectricity caused by noxious stimulation（ P < 0. 05）

and the number and density of c-fos positive neurons in the nucleus tractus solitarii were significantly decreased（ P < 0. 05）. The 1 mA EA at"Zusanli"（ ST36） and"Quchi"（ LI11） did not significantly improve the rectus abdominis myoelectrical delivery caused by CRD. 3 mA EA at "Zusanli"（ ST36） and "Tianshu"（ ST25）significantly inhibited the activity of EMG induced by CRD（ P < 0. 01）

and also significantly reduced the number and fluorescence intensity of c-fos positive neurons in nucleus tractus solitarii（ P < 0. 05）. Conclusion EA at"Tianshu"（ ST25） and"Zusanli"（ ST36） significantly inhibited the nociceptive response induced by CRD

and decreased the expression of c-fos positive neurons in nucleus tractus solitarii of rats. In the same segment of the spinal cord

EA at "Tianshu"（ ST25） needed less intensity to produce inhibitory effects.