A new method using flow cytometry to measure the effects of drugs on gastric emptying and gastrointestinal transit in mice

The use of radiolabelled markers is considered to be a gold standard for assessing gastric emptying and gastrointestinal transit in mice and rats, but their use has increasingly been restricted due to health concern. Therefore, a new method using fluorescent polystyrene microbeads and flow cytometry was devised. Saline containing fluorescent markers (together with non-fluorescent microbeads) was infused into the stomach of each mouse and gastric emptying and gastrointestinal transit were calculated by measuring the quantity of the fluorescent microbeads in the gastrointestinal tract using flow cytometer. The effects of saline (as a control), morphine (CAS 52-26-6) and dexmedetomidine (CAS 113775-47-6) were tested. Both gastric emptying and gastrointestinal transit measured with this method (after i.p. injection of saline) were similar to those reported previously using the conventional radiolabelled methods. Morphine significantly inhibited both gastric emptying and gastrointestinal transit in a dose-dependent manner. Dexmedetomidine did not significantly inhibit gastric emptying but inhibited gastrointestinal transit. These results were also similar to those obtained using the conventional radiolabelled method. The method using fluorescent microbeads and flow cytometry may be a reliable alternative to the methods using radioisotope for studying the effects of drugs on gastric emptying and gastrointestinal transit.