[Effects of acupoint area and non-acupoint area of eye-acupuncture on expressions of VIP and AQP 8 in colonic tissues in rats with D-IBS].

OBJECTIVE: To explore the point specificity of eye-acupuncture and the mechanism of eye-acupuncture on diarrhea-predominant irritable bowel syndrome (D-IBS). METHODS: Forty male Wistar rats of SPF grade were randomly divided into a normal group, a model group, a eye-acupuncture point (AA) group and a non-point (NA) group. The D-IBS rat model was established with the combination methods of the chronic stress and binding limbs. The AA group was treated by acupuncture at "low energizer area", "large intestine area", "liver area" and "spleen area", and the NA group by acupuncture at 3 mm apart from the same points area mentioned above, and the normal group and the model group with no intervention. The rate of feces moisture content was detected. Reverse transcription-polymerase chain reaction (RT-PCR) was used to detect the mRNA of aquaporin 8 (AQP 8) in colon. Protein expressions of the vasoactive intestinal peptide (VIP) and AQP 8 in colon were detected by SABC immunohistochemistry method. RESULTS: Compared with normal group, the rate of feces moisture content at the 18th and 25th days, VIP protein in colon mucosa, myenteric nerve plexus and hypo-mucosa nerve plexus increased significantly (all P < 0.01), and AQP 8 mRNA in colon mucosa decreased significantly in model, AA and NA group (P < 0.05, P < 0.01); AQP 8 protein in colon mucosa decreased significantly in model group and NA group (both P < 0.01). Compared with model group, the rate of feces moisture content at the 25th day and VIP protein in colon mucosa decreased significantly (P < 0.01, P < 0.05), and AQP 8 mRNA and protein increased significantly (P < 0.05, P < 0.01) in AA group. Compared with AA group, the rate of feces moisture content at the 25th day and VIP protein in colon mucosa increased significantly (both P < 0.01), and AQP 8 mRNA and protein decreased significantly (both P < 0.01) in NA group. CONCLUSION: Eye-acupuncture has a good therapeutic effect on D-IBS. It is suggested that one of the mechanism is relate to increase AQP 8 in colon tissue and restrain the expression of VIP. Non-point area of eye-acupuncture has no obviously therapeutic effect and so to illustrate the point specificity of eye-acupuncture.