OBJECTIVE: To observe the effect of electroacupuncture (EA) on intestinal epithelial mucosal barrier function in diarrhea-predominant irritable bowel syndrome(IBS-D) rats, so as to explore its mechanisms underlying improvement of IBS-D. METHODS: Forty SD rats (half male and half female) were randomly divided into control, model, EA and medication (Pinaverium Bromide, PB) groups, with 10 rats in each group. The IBS-D model was established by chronic unpredictable mild stress combined with gavage of Senna-leaf solution. EA (2 Hz/15 Hz，0.1-1 mA) was applied to unilateral "Zusanli"(ST36),"Tianshu" (ST25), "Sanyinjiao"(SP6) and "Taichong"(LR3) alternatively for 15 min, once daily for 14 days. Rats of the medication group was treated by gavage of PB (10 mL·kg·d) for 14 days. The visceral sensitivity (pain) was assessed by using the pressure threshold which the inserted rectal balloon catheter air-inflation (connected to a blood pressure gauge) induced stronger abdominal muscular contraction to force the rat's abdomen to lift the experimental stand surface. The diarrhea index was used to evaluate loose stool grade. The expression of Claudin-1 and Occludin (intestinal epithelial tight junction proteins) of colon tissue was detected by immunohistochemistry. The activity of plasma diamine oxidase (DAO) was assayed by using spectrophotometry. RESULTS: Compared with the control group, the diarrhea index and plasma DAO activity in the model group were significantly increased (<0.01), while the visceral pain threshold, expression of Claudin-1 and Occludin in the model group were significantly decreased (<0.01). After the treatment, the diarrhea index and plasma DAO activity were significantly lower in both EA and medication groups than that in the model group (<0.01), and the visceral pain threshold and expression levels of Claudin-1 and Occludin were obviously increased (<0.05, <0.01). No significant differences were found between the EA and medication groups in all the above-mentioned indexes (>0.05). CONCLUSION: Electroacupuncture can significantly improve abdominal pain and diarrhea in IBS-D model rats, which may be closely associated with its effects in up-regulating the expression of intestinal epithelial tight junction proteins Claudin-1 and Occludin to restore the function of intestinal epithelial mucosal barrier.