Improvement and Evaluation of Rat Model of Diarrhea-predominant Irritable Bowel Syndrome Induced by Chronic Restrain Stress / 广州中医药大学学报

ABSTRACT

Objective To modify the rat model of diarrhea-predominant irritable bowel syndrome(IBS-D) induced by chronic restrain stress,and to evaluate the modified model. Methods Thirty specific-pathogen free Sprague Dawley rats were randomly divided into control group,one-hour model group and 2-hour model group, 10 rats in each group and half being male. One-hour model group and 2-hour model group were given restrain stress one, 2 hour (s)per day respectively, and the treatment lasted 14 days. On day 7, 14, 21, 28 after modeling,the number of feces grains within 4 hours,area of the excrement and body mass were monitored. On modeling day 28 , abdominal withdrawal reflex (AWR) scores for visceral sensitivity were calculated , the pathological features of gastric antrum, duodenal, ileac, colonic tissues were observed by hematoxylin-eosin staining, and the expression level of 5-hydroxytryptamine-3A receptor (5-HT3AR) in rat colon tissue was detected by real time quantitative polymerase chain reaction(qPCR). Results Compared with control group,the number of feces grains in one-hour model group showed no obvious changes on day 7, 14, 21, 28, but the area of the excrement was obviously increased and body mass was decreased on day 14 (P < 0.05 or P < 0.01);in 2-hour model group,the number of feces grains and area of the excrement were increased on day 21,28, and body mass was decreased obviously on day 7,14,21,28 (P < 0.05 or P < 0.01). One-hour model group and 2-hour model group had higher AWR scores than the control group (P < 0.05),but the difference between the two model groups was insignificant(P > 0.05). The optical microscopy results showed that no various changes in gastric, duodenal, ileac, colonic tissues in the two model groups as compared with those in the control group. QPCR results showed that the expression level of 5-HT3AR in rat colonic tissues of the two model groups was higher than that of the control group (P < 0.05), but the expression level of 5-HT3AR in rat colonic tissues of model was not significantly different from that of the control group(P > 0.05). Conclusion IBS-D model can be successfully established with chronic restrain stress for 2 hours per day and lasting for 14 days. Excrement area and AWR scores can be used as the objective indexes for the evaluation of IBS-D model.