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 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.

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 (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.

Conclusions & Inferences

This novel approach provides a reliable, automatic and low-cost method of measuring gastrointestinal transit time in mice.

Images (jpg) are sequentially numbered and were taked at 5min intervals.

Matlab code automatically counts fluorescent boli.

See extensive notes within matlab m file: automated_gut_transit_measure_1_9_20.m