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Action potential characterization in intact mouse heart: steady-state cycle length dependence and electrical restitution | Author(s) | Björn C. Knollmann, Tilmann Schober, Andreas O. Petersen, Syevda G. Sirenko, and Michael R. Franz | | Journal | Am J Physiol Heart Circ Physiol, 292 | Method Extract | | ... ...at 37C in the normal Tyrode solution. Fluorescence signals of fluo-3 were detected by a fluorescence system interface (IonOptix). The fluo-3-loaded cells were excited at 488 nm with a xenon arc lamp, and the emitted fluorescence was measured at a... ... | Abstract | | Transgenic mice have been increasingly utilized to investigate the molecular mechanisms of cardiac arrhythmias, yet the rate dependence of the murine action potential duration and the electrical restitution curve (ERC) remain undefined. In the present study, 21 isolated, Langendorff-perfused, and atrioventricular node-ablated mouse hearts were studied. Left ventricular and left atrial action potentials were recorded using a validated miniaturized monophasic action potential probe. Murine action potentials (AP) were measured at 30, 50, 70, and 90% repolarization (APD30–APD90) during steady-state pacing and varied coupling intervals to determine ERCs. Murine APD showed rate adaptation as well as restitution properties. The ERC time course differed dramatically between early and late repolarization: APD30 shortened with increasing S1–S2 intervals, whereas APD90 was prolonged. When fitted with a monoexponential function, APD30 reached plateau values significantly faster than APD90 ( = 29 ± 2 vs. 78 ± 6 ms, P < 0.01, n = 12). The slope of early APD90 restitution was significantly <1 (0.16 ± 0.02). Atrial myocardium had shorter final repolarization and significantly faster ERCs that were shifted leftward compared with ventricular myocardium. Recovery kinetics of intracellular Ca2+ transients recorded from isolated ventricular myocytes at 37°C ( = 93 ± 4 ms, n = 18) resembled the APD90 ERC kinetics. We conclude that mouse myocardium shows AP cycle length dependence and electrical restitution properties that are surprisingly similar to those of larger mammals and humans. |
Our Ref: 1414
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