Acetylcholine Reduces IKr and Prolongs Action Potentials in Human Ventricular Cardiomyocytes

Figures

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  Figure 1. (a) Human left ventricular myocardial slice: superimposed recording of action potentials (APs) during control and after 3 min superfusion with ACh (5 µM) at a BCL of 1000 ms; (b) human right ventricular papillary muscle: superimposed recording of APs during control and after 3 min exposure to ACh (5 µM) at a BCL of 1000 ms; (c) human right ventricular Purkinje fiber: superimposed recording of an AP during control and after 3 min exposure to ACh (5 µM) at a BCL of 500 ms. Note that ACh slightly prolongs repolarization. AP waveform recordings originate from the same preparation and same impalement. Panel a depicts APs recorded from a non-diseased human donor heart; panels b and c depict APs recorded from a human donor heart with 29% ejection fraction.

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  Figure 2. Optical recordings of human left ventricular myocardial slice. (a) Superimposed optical mapping recording of human left ventricular APs during control (‘base’) and after superfusion with ACh (5, 10, and 15 µM) at a BCL of 1000 ms. (b) AP duration at 30, 50, and 80% repolarization (APD30, APD50, and APD80, respectively) under control conditions and after superfusion with ACh at a BCL of 1000 ms.

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  Figure 3. ACh reduces the rapid delayed rectifier K+ current (IKr) in hiPSC-CMs. (a) Typical current traces in response to 4 s long depolarizing pulses from a holding potential of −50 mV under baseline conditions (left panel) in presence of 5 µM ACh (middle panel) and in additional presence of 5 µM E4031 (right panel). (b) Typical E4031-sensitive currents obtained from the currents in panel a under baseline conditions and in the presence of ACh. (c) Current–voltage (I–V) relationships of the E4031-sensitive current during the depolarizing steps. (d) I–V relationships of the E4031-sensitive current during the tail. Insets: average V1/2 (membrane potential for the half-maximal activation) and k (slope factor) of the voltage-dependence of activation. (e) Average time constants of activation (Act) and deactivation (Deact). * p < 0.05.

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  Figure 4. ACh prolongs APs in a frequency-dependent way. (a) Typical APs (top panel) and their first derivative of the AP upstroke (inset) and repolarization phases (bottom panel) at 1 Hz under baseline conditions and in presence of 5 µM ACh. (b) Average AP parameters at 1 Hz under baseline conditions and in presence of 5 µM ACh. (c) Typical APs (top panel) and their first derivative of the AP upstroke (inset) and repolarization phases (bottom panel) at 3 Hz under baseline conditions and in presence of 5 µM ACh. (d) Normalized effects of ACh on APs recorded at 1 and 3 Hz. RMP: resting membrane potential; Vmax: maximal AP upstroke rate; APA: AP amplitude; APD20, APD50, APD90: AP duration at 20, 50, and 90% repolarization, respectively; phase-3: maximal phase-3 repolarization rate. * p < 0.05.

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  Figure 5. Functional effects of the ACh-induced reduction in IKr on a model human ventricular cardiomyocyte (O’Hara–Rudy human ventricular cell [27]). (a) APs (top) and associated IKr (bottom) at a stimulus frequency of 1 Hz. (b) APs (top) and associated IKr (bottom) at a stimulus frequency of 3 Hz. (c) AP duration at 50% and 90% repolarization (APD50 and APD90, respectively) at stimulus frequencies ranging from 0.5 to 3.0 Hz. (d) Human left ventricular myocardial slice: superimposed recording of APs during control and after superfusion with dofetilide (50 nM) at a BCL of 1000 ms.