Different paths, same destination: divergent action potential responses produce conserved cardiac fight‐or‐flight response in mouse and rabbit hearts

Cardiac electrophysiology and Ca2+ handling change rapidly during the fight‐or‐flight response to meet physiological demands. Despite dramatic differences in cardiac electrophysiology, the cardiac fight‐or‐flight response is highly conserved across species. In this study, we performed physiological sympathetic nerve stimulation (SNS) while optically mapping cardiac action potentials and intracellular Ca2+ transients in innervated mouse and rabbit hearts. Despite similar heart rate and Ca2+ handling responses between mouse and rabbit hearts, we found notable species differences in spatio‐temporal repolarization dynamics during SNS. Species‐specific computational models revealed that these electrophysiological differences allowed for enhanced Ca2+ handling (i.e. enhanced inotropy) in each species, suggesting that electrophysiological responses are fine‐tuned across species to produce optimal cardiac fight‐or‐flight responses.

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