Background: 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.
Methods: Naïve mice (n = 20) were gavaged with a non-caloric viscous suspension of 4.4% fluorescent dye 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.
Results: Fluorescent boli were detected with high sensitivity, while unstained boli were readily rejected. All cages showed no fluorescent boli for the first ~20 frames (100 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 = .95 ± .02), being robust to parameter changes.
Conclusions and inferences: This novel approach provides a reliable, automatic, and low-cost method of measuring gastrointestinal transit time in mice.
Keywords: fluorescence; fluorescent imaging; gastrointestinal transit; motility; transit time.
© 2020 John Wiley & Sons Ltd.