The principles behind our membrane potential assays are as follows:

Cells are incubated with a membrane potential dye-loading solution, which allows the membrane potential indicator to penetrate into cells. Upon entering cells, the fluorescence intensity of the indicator significantly enhances.  Once there is an ion channel opening, the dye will follow the ions and go out of the cells resulting in a fluorescence signal decrease or the dye will further accumulate inside the cells resulting in a fluorescence signal increase.