Abstract
.Infrared control is a new technique that uses pulsed infrared lasers to thermally alter electrical activity. Originally developed for nerves, we have applied this technology to embryonic hearts using a quail model, previously demonstrating infrared stimulation and, here, infrared inhibition. Infrared inhibition enables repeatable and reversible block, stopping cardiac contractions for several seconds. Normal beating resumes after the laser is turned off. The block can be spatially specific, affecting propagation on the ventricle or initiation on the atrium. Optical mapping showed that the block affects action potentials and not just calcium or contraction. Increased resting intracellular calcium was observed after a 30-s exposure to the inhibition laser, which likely resulted in reduced mechanical function. Further optimization of the laser illumination should reduce potential damage. Stopping cardiac contractions by disrupting electrical activity with infrared inhibition has the potential to be a powerful tool for studying the developing heart.
Highlights
Infrared control is a new technique that uses pulsed infrared lasers to thermally alter electrical activity
Infrared control was first developed as infrared neural stimulation and uses pulsed infrared laser light to elicit firing of an action potential[2] through a thermal effect,[3] where the rapid temperature changes affect membrane capacitance[4] and mitochondrial calcium cycling.[5,6]
We have recently shown that infrared control can be used to inhibit electrical activity.[14]
Summary
Infrared control is a new technique that uses pulsed infrared lasers to thermally alter electrical activity. We demonstrate reversible infrared inhibition of early embryonic avian hearts, both in intact embryos and excised hearts, with spatial selectivity, and we further investigate the target of inhibition and potential damage. By contrast, positioning the inhibition laser on the atrium resulted in blocking the initiation of contraction, resulting in the abolition of motion in the entire heart [Fig. 2(b)].
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