An automated sensitive approach for measuring whole gut transit time

Background <p>Commonly used methods to measure whole gut transit time in rodents have yet to combine high sensitivity, objectivity and automation. We have developed a novel method using oral gavage of non-toxic fluorescent dye particles and their detection by fluorescence imaging to enable unbiased automated detection of gut transit time simultaneously in 8 cages.</p> Methods <p>Naïve mice (n=20) were gavaged with a 4.4% suspension of fluorescent dye in CMC in 3 groups on 2 occasions. Each group was imaged in 8 cages at 5-minute intervals using blue LEDs for illumination and a Sony full-frame mirrorless camera with a green band-pass emission filter. Custom Matlab code counted the number of fluorescent boli per cage post-hoc and provided graphical and spreadsheet output. Boli counts across a wide range of parameters were compared to blind assessments by an experimenter.</p> Results <p>Fluorescent boli were detected with high sensitivity, while unstained boli were readily rejected. All cages showed no fluorescent boli for the first ~20 frames (120 minutes), after which many cages gradually show a rise to 1-6 fluorescent boli. The mean time to first fluorescent bolus in each session was 264±141 and 223±81 minutes post-gavage, with no within subject consistency. There was high correlation between automated scores and that of experimenter (r=0.95±0.02), being robust to parameter changes.</p> Conclusions &amp; Inferences <p>This novel approach provides a reliable, automatic and low-cost method of measuring gastrointestinal transit time in mice.</p>