Etiology of irritable bowel syndrome

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To get insight into Pathophysiology of irritable bowel syndrome (IBS) we measured simultaneously motility and transepithelial potential difference (PD) in normal and IBS colon in vivo. In normal colon: 1) Colonic contractions are mostly sporadic except in the rectum where a periodic motor activity (amplitude, 10-30 cm H_2O; frequency, 3-4 cycle/s; duration, 10-30 min; interval, 70-100 min) was observed; 2)PD was highly variable among individuals (10--50mV) but was not different in the colonic segments between the transverse colon and rectum in each individual; 3)In about 30% of total events, contraction was associated with an increase in PD, presumably reflecting the activation of Cl secretion; 4)Distention of colonic wall caused an increase in PD. In IBS colon: 1)Motility was not noticeably different from that in the normal colon; ZTPD was extremely high for diarrhea-type IBS whereas it was rather small for constipation-type IBS. In addition, using rat distal colon in vitro, we demonstrated that distention of the colonic wall causes an increase in mucosal Cl secretion through the activation of submucosal neurons. Further investigation utilizing the present methods would reveal critical roles of disordered activation of motility and Cl secretion for the pathophysiology of IBS.