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

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Abstract
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 15-30 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 5 photodectectors the action potentials from 5 different regions of the preparation were monitored simultaneously. 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. The optical method can validly be used to solve some problems on arrhythmia-related mechanism.