A novel method for the evaluation of intestinal transit and contractility in mice using fluorescence imaging and spatiotemporal motility mapping

Abstract

This study introduces a novel, simplified method for the evaluation of murine intestinal transit and contractility using fluorescence and video imaging. Intestinal transit was measured by evaluating the intestinal distribution of non-absorbable fluorescein-labelled dextran (70 kDa, FD70) along the gastrointestinal (GI) tract. After excision of the GI tract, two full-field images--one in normal illumination mode and another in fluorescent mode--were taken with a charge coupled device (CCD) camera and subsequently matched for calculation of fluorescence distribution along the GI tract. Immediately after, intestinal contractility was evaluated in different regions of the intact intestine by spatiotemporal motility mapping (i.e. video imaging). In control mice, the small intestine showed vigorous oscillatory contractions and FD70 was primarily distributed within the terminal ileum/caecum at 90 min postgavage. As validation step, the effect of intestinal manipulation (IM, surgical procedure) and two pharmacological agents--known to alter GI motility--was tested. At 24 h postoperatively, spontaneous contractile activity of the small intestine was nearly abolished in IM mice, leaving the small intestine distended and resulting in a significantly delayed intestinal transit. In accordance, spontaneous mechanical activity of circular muscle strips in standard organ baths was significantly reduced in IM mice compared to control mice. Administration of atropine (1-3 mg kg(-1), i.p.) suppressed spontaneous contractile activity along the entire intestinal tract and induced a dose-related delay in intestinal transit. In contrast, metoclopramide (3-10 mg kg(-1), i.p.) markedly increased contractile activity--however only in the upper GI tract--and accelerated intestinal transit in a dose-dependent manner.