| OBJECTIVE The present study was carried out to establish the model of slow transit constipation by feeding rats with diphenoxylate. Then we study the pathogenesis of slow transit constipation by investigating the changes of interstitial cells of Cajal in the colon of model rats.METHODS Thirty-two healthy Wistar rats were randomly divided into control group and model group of slow transit constipation. The rats in model group received daily diphenoxylate(8mg·kg-1d-1)by irrigation stomach method to develop the slow transit constipated model. Record the fecal data and the weight of each rat every 5 days. After 100 days, intestinal transit functions were examined by activated charcoal pushing test. At last, the rats were killed, and the colonic tissues 5cm apart from cecum were cut. The expression of ICC was detected by immunohistochemistry and the alteration was analysed by the computer image analysis system.RESULTS The fecal data of model rats was significantly smaller than that of the normal rats (P <0.05). The movement of contents from the proximal to the distal colon and rectum in model group were significantly slower than those in normal group. In model rats, the time of discharge of the first black fecal was (686±57)min, significantly longer than that in normal rats (608±46)min(P <0.05). Colon tissue c-kit+cell,s area in model rats was significantly reduced than that of normal rats (P <0.05). This reduction was most significant in the ICC between the inner and outer layers of the muscularis propria [( 11.497±2.692)×104μm2 VS(23.709±3.907)×104μm2 , P <0.01].CONCLUTIONS 1. The model of rats with slow transit constipation is successfully established. 2. Pathological changes of colonic interstitial cells of Cajal occure in rats with slow transit constipation, including the number and the network structure. 3. Abnormality of distribution and numbers of interstitial cells of Cajal may be a reason of slow transit constipation.
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