Abstract
Hamsters are frequently studied as a model of cardiomyopathy, but the electrophysiological properties of a hamster heart are not well defined. We examined rate-dependent changes in action potentials and underlying ionic mechanisms in isolated ventricular myocytes from hamster hearts using the whole-cell configuration of the patch clamp technique. At 0.1 Hz stimulation, the mean action potential duration at 90% (APD90) and 20% (APD20) repolarization were 63±7 ms and 9±1 ms, respectively (n=17). With increasing frequency of stimulation, APD progressively prolonged to 119±16 ms (APD90) and 36±7 ms (APD20) at 6.0 Hz. A further increase in the rate of stimulation to 8.0 Hz did not change APD significantly. Application of 4 mM 4-aminopyridine (4-AP) lengthened APD markedly and completely prevented the rate-dependent prolongation. Cd2+ (0.2 mM) shortened APD and generally attenuated the rate-dependent lengthening of APD up to 5.0 Hz, but unaffected the lengthening of APD with the further increase in the rate. At plateau voltages, there were two time-dependent currents, I to1 and I Ca,L. Recovery from inactivation for I to1 had two components: t slow=980±129 ms accounting for 58% of the total fraction, and t fast=39±13 ms (n=7). Recovery from inactivation for I Ca,L was rapid with t=20±4 ms (n=6). Results suggest that the slow recovery from inactivation in I to1 is the main reason for the rate-dependent prolongation of APD in hamster ventricular myocytes.
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Kocic, I., Hirano, Y. & Hiraoka, M. Rate-dependent changes in action potential duration and membrane currents in hamster ventricular myocytes. Pflügers Arch - Eur J Physiol 443, 353–361 (2002). https://doi.org/10.1007/s004240100683
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DOI: https://doi.org/10.1007/s004240100683