Objective: To investigate changes of activities of c fos and nitric oxide synthase (NOS) in visceral afferent pathway during gastric experimental inflammation pain and following electroacupuncture (EA). Methods: A total of 30 SD rats were evenly randomized into control group

inflammatory pain group (model group) and EA group. Inflammatory pain model was generated by intragastric infusion of formaldehyde plus normal saline. “Zusanli" (ST 36) was punctured and stimulated electrically (1～5 V

4～16 Hz) for 60 min. Immonohistochemical staining techniques were used to detect the activities of c fos and NOS in the nodose ganglion(NG)

dorsal root ganglion(DRG)

spinal cord(SC)and the nucleus of the solitary tract(NTS)during gastric inflammation pain and after EA. Results: In comparison with control group

the number of c fos immuno reaction (IR) positive neurons in NTS X of model group and EA group was significantly bigger ( P <0.01); while that of EA group was significantly smaller than that of model group ( P <0.01). No significant changes were found in SC of the 3 groups. The proportions of NOS positive (stronger and moderate positive) neurons of NG and DRG in model group were significantly lower than those of control group ( P <0.01)

while those of NOS positive (stronger

moderate and weaker positive) neurons in NG and DRG of EA group were significantly higher than those of model group ( P <0.01). It shows that NO may be involved in the afferent process of gastric pain signals ascending to the brain stem by way of visceral sensory pathway along the vagus nerve

and EA may reduce pain induced expression of NOS and c fos.Conclusion: EA can resist gastric nociceptive stimulation generated increase of NOS and c fos activities. The descending inhibitory pathway existing in the spinal cord may check the ascending transmission of the visceral nociceptive information.