Optical recording of conducted action potential in heart muscle using a voltage-sensitive dye

The absorption signals of a merocyanine-rhodanine dye in response to action potential were measured on the bullfrog atrium. Simultaneous recording of optical signals and membrane potential showed the same time course within 15 to 30 min after exposure to Ca2+- free solution. The action spectrum of the dye exhibited a triphasic pattern with a decrease in absorption between 530 and 600 nm, an increase between 640 and 720 nm and a decrease at 750 nm. Using five photodetectors we have able to simultaneously monitor the action potential from five different regions of the preparation. The conduction velocity could be measured even in Ca2+- free solution; the velocity measured optically by the simultaneous multi-recording method was equal to that obtained with a microelectrode measurement. Thus, the optical method can validly be used to solve some problems on arrhythmia-related mechanism.