| [Background and Aims] The irritable bowel syndrome (IBS) is a functional bowel disorder characterized by abdominal pain/discomfort and altered bowel habits. The change of bowel sensitivity possibly involved in the IBS is considered as an important mechanism currently. It is extremely difficult to obtain tissues or cells for the study on bowel sensitivity in IBS patients as IBS is referred to a functional disorder. Therefore, it is necessary to set up a model of IBS for exploring the IBS pathogenesis. However, an ideal model of IBS is not available now, especially the model of constipation-predominant IBS (C-IBS) which is a major subtype of IBS. In this experiment, a new model of C-IBS was created by stomach irritation of cool water which imitated one of the risk factors of IBS patients-drinking cool water. The change of bowel sensitivity was evaluated and the possible molecular mechanism was studied, which show a new clue or evidence for the mechanism of bowel sensitivity alteration.[Methods] Wistar rats of postnatal four weeks were divided into three groups: group A (stomach irritation of 0-4 C cool water),group B(stomach irritation of room temperature water)and group C(control group). The rats in both group A and group B received cool water irritation daily for fourteen days. In these fourteen days, the feces of rats in three groups were collected and the feces granules were counted, moisture contents were calculated daily during 0 to 3 hour and 3 to 24 hour respectively. After suspending the irritation of cool water, the feces granules and moisture contents of feces were continuously investigated for the followingfourteen days in order to evaluate the degree of constipation. And then, the perception thresholds and the number of abdominal withdrawal reflexes (AWR) were recorded when rectal balloon distention was performed. This procedure was used to evaluate bowel sensitivity. The concentrations of 5-HT, LTB4, HA and BK in serum were measured by enzyme linked immunoadsorbent assay (ELISA). The ileocecal junction and colon samples were stained by Haematoxylin-Eosin (HE) for routine pathologic examination and the improved toluidine blue method for mast cells, respectively. The distribution of NGF in bowel was showed by immunohistochemical staining, and the NGF expression was analyzed by computer color image analyzer at semi-quantity.[Results] The granules and moisture contents of feces were significantly higher in group A than group B and group C during 0 to 3 hour after cool water irritation (P<0.05) , but the differences disappeared after suspending irritation (P>0.05). During the primary fourteen days, the granules of feces decreased from 49.37 + 7.46 to 39.90 + 6.23 during 3 to 24 hour after cool water irritation in group A (48.85+6.51 to 41.44+7.62 in group B, 49.53 + 7.19 to 50.80 + 8.72 in group C). At 15th day, cool water irritation stopped. The granules of feces were 42.90+ 6.71 in group A, 43.89+7.91 in group B and 49.5+5.76 in group C at 28th day, respectively. During irritation and suspending irritation, the granules of feces in group A were significantly lower than those in group B and group C during 3 to 24 hour (P<0.05) . During the primary fourteen days, the moisture contents of feces decreased from 45.21%+5.77% to 40.28%+6.47% in group A, 43.00% + 6.52% to 44.74%+6.37% in group B, 46.23%+7.98%to 42.47%+9.42% in group C during 3 to 24 hour after cool water irritation. At 28th day, the moisture contents were 39.86%+6.53% in group A, 46.60%+4.44% in group B and 47.14%+8.58% in group C during 3 to 24 hour, respectively. During irritation and suspending irritation, the moisture contents of feces were significantly lower in group A than those in group B and group C during 3 to 24 hour (P<0.05) .The perception threshold was 0.59 +0.09ml in group A , which was higher than group C (0.57 + 0.13ml)during rectal balloon distention, but there is no significant difference between two groups (P>0.05) . The number of abdominal withdrawal reflexes (AWR) to balloon distention with 1.0ml... |
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