Idiopathic inflammatory bowel disease (IBD) is associated with the gastrointestinal dysmotility. In the inflamed proximal colon isolated from 2, 4, 6-trinitrobenzenesulfonic acid (TNBS)-induced Crohn's disease model rat, motility index, amplitude and frequency of sponraneous contractions were decreased. Because rhythmic contraction is close by associated with the activity of pacemaking cell (interstitial cell of Cajal; ICC) and myenteric nerve system, we investigated whether these functional changes are related to the morphological changes in ICC, myenteric nerve system and muscularis resident macrophages using the TNBS-induced inflamed colon. In TNBS-treated colon, the network of ICC was disappeared or broken. Furthermore, myenteric nerve system also changed morphologically in the inflamed region. The number of muscularis resident macrophage in myenteric region significantly increased and the shape of macrophage rounded at a region where the ICC disappeared. These results suggest that inhibition of spontaneous contractions in curcular smooth muscle from TNBS-induced colitis rat colon is attributable to the morphological changes of ICC and myenteric nerve system, and muscularis resident macrophage may be involved in these changes.