We intended to characterize the effect of inflammation on the spontaneous colonic motility pattern and the role of iNOS in its disruption in colitis. Colitis was induced by an intracolonic enema of T. spiralis larvae. Animals were studied 2-30 days postinfection (PI). Standard H&E and iNOS staining was performed on colonic sections. Altered stool consistency was found from day 1 to day 21 PI; leukocytosis peaked on days 6-21 PI. Edema and cell infiltration were found in mucosa and submucosa (days 2-14 PI). Contractility displayed a disorganized pattern with decreased high-amplitude, low-frequency (HALF) contractions. A progressive fading of spontaneous activity was observed and was partly restored in strips devoid of submucosa. iNOS immunoreactivity increased in epithelial and infiltrating cells (days 2-14 PI). In this model of colonic inflammation, the decrease in spontaneous contractility, which might be caused by NO generated from mucosal and submucosal iNOS, bears some traits with changes observed in ulcerative colitis and might thus be useful to study the dismotility observed in this human disease. © 2005 Springer Science+Business Media, Inc.