[Electric activation of the heart using laser spectrometry. 1. Study of transmembrane action potentials using optical...

The action potentials of the contractile myocardium and conduction cells are usually recorded by intracellular glass microelectrodes but they call also be obtained at a distance and without physical contact by optical techniques. The myocardial fragment must be stained with a dye which, when illuminated by a laser beam, emits a fluorescence whose wave length is related to the transmembrane potential. The responses obtained were checked by microelectrode and optical techniques on several types of preparation (sheep myocardium, sheep Purkinje cells, mouse myocardium). The morphology of the action potential was identical by both methods; the beginning of phase 0 in particular was identical with both methods, eliminating any mechanical activity. Contraction appeared later, during the plateau phase of the action potential with a measurable interval corresponding to the excitation- contraction coupling time. Remote recordings of action potentials without physical contact with the preparation, should enable very accurate myocardium activation mapping using CCD video techniques.