The use of fluorescent dyes to measure membrane potentials: a critique

Under controlled conditions, fluorescent cyanine dyes can be used to measure membrane potentials of cell suspensions. Similar changes in membrane potential can be followed both with fluorescent dyes and electrophysiological probes in response to changes in the ion composition of the medium. Recent reports that attempt to abrogate the use of the cyanine dyes in measurements of the membrane potential are misleading.