Localization of pacemaking activity in early embryonic heart monitored using voltage-sensitive dye

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Abstract
Potential sensitive dye-related absorption signals provide a new method for monitoring spontaneous action potential activity in the early embryonic heart. This technique is based on the observation that changes in potential across membrane(s) stained with certain voltage-sensitive dyes are accompanied by changes in their optical properties (absorption, fluorescence and/or birefringence). Absorption signals demonstrated, in embryonic pre-beating chick heart in the 7-8-somite stages, the occurrence of action potential activity, development of pacemaker potential and cardiac rhythm generation. With this method, originally introduced to record neuronal activity in invertebrate ganglia, many cells or portions of the preparation can be monitored simultaneously. The optical recording apparatus was expanded to monitor simultaneously spontaneous action potentials from 5 portions of an early embryonic hearts of chicks (white Leghorn) at the 7-11 somite developmental stages, corresponding to 25-35 h of incubation. The hearts attached to the embryo were stained with a merocyanine-rhodanine dye (NK2761) as a potentiometric probe. This dye is an analog of dye XVII or dye XXIII.