Assessment of visceromotor responses to colorectal distension

Assessment of visceromotor responses to colorectal distension was performed at 5 weeks after the exposure to juvenile SDS. As a visceral stimulus, mechanical distensions of the rectum were performed by pressure-controlled air inflation of a flexible polyethylene balloon connected to an electronic distension device (Distender Series II barostat, G&J Electronics, Willowdale, ON, Canada). The balloon was lubricated, inserted intra-anally and positioned 5 mm proximal to the anus. The visceromotor responses to colorectal distension were quantified by electromyographic recordings of abdominal wall muscle activity. Mice were challenged with distending pressures of 15, 30, 45, and 60 mmHg, with two 10-s trials at each pressure and a 2-min recovery period between distensions. Data were imported into 8-channel analyzer software (Starmedical, Tokyo, Japan) for analysis. Representative raw electromyographic recordings are depicted in mV. The electromyographic baseline activity during the 10-s before stimulation was subtracted from the 10-s of each reflex response.