Antiarrhythmic Properties of Elsholtzia ciliata Essential Oil on Electrical Activity of the Isolated Rabbit Heart and Preferential Inhibition of Sodium Conductance

Figures

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  Figure 1. E. ciliata effects on the pseudo ECGs of Langendorff-perfused rabbit hearts. Epicardial pacing with a 300 ms period was applied. (A) Superimposition of steady-state pseudo ECG traces under control conditions (CON; black) and after application of 0.01, 0.03, 0.1 and 0.3 µL/mL concentrations of E. ciliata (orange, grey, yellow and blue, respectively) for 10 min each, followed by perfusion without E. ciliata (WO; dotted). Q, R, S, and T waves indicated. Notice a lengthened time-to-Rmax and shortened QT interval as indicated by dotted arrows 1 and 2, respectively. (B) Three-dimensional (3D) view of pseudo ECGs, from front to back, showing time-dependent effect of increasing concentrations of E. ciliata from the same data as in (A), constructed by LabChart8 Pro software ECG analysis plot function, in which the X, Y and Z axis represent location, time, and height of the detected peaks of the pseudo ECG, respectively. Wave amplitudes are indicated by colors from blue to red. (C) Mean data of QRS (upper) and QT (lower) interval change when applying different E. ciliata concentrations as indicated (* p < 0.05 for E. ciliata vs. control; # p < 0.05 for washout vs. E. ciliata of 0.3 µL/mL…

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  Figure 2. E. ciliata effects on the action potentials (APs) of Langendorff-perfused rabbit heart. Epicardial pacing with a 300 ms period was applied. (A) Superimposition of representative traces of APs from microelectrodes, from the same experiment as in Figure 1, under control conditions (CON; black) and after application of 0.01, 0.03, 0.1, and 0.3 µL/mL concentrations of E. ciliata (orange, grey, yellow and blue, respectively), followed by washout without the E. ciliata (WO; dotted). (B) Three-dimensional (3D) view of APs, from front to back, showing time-dependent effect of E. ciliata from the same data as in (A); 3D view construction details are the same as in Figure 1B. (C) Values of the maximal velocity of APs upstroke (dV/dtmax) after application of E. ciliata concentrations as indicated from the same experiment as in (A).

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  Figure 3. Dependence of the AP parameters on E. ciliata concentrations. Steady-state level measurements during atrial/endo-/epi-cardial stimulation (300 ms period) of (A) activation time, (B) the maximal velocity of AP upstroke depolarization (dV/dtmax), (C) AP duration (APD) at 20%, 50% and 90% repolarization, and (D) resting potential (RP), measured under control conditions (CON) and at the end of 10 min perfusion with each of 0.01, 0.03, 0.1 µL/mL concentrations of the E. ciliata (except for 0.3 µL/mL, which was ~5 min), followed by a washout period (WO) (* p < 0.05 for E. ciliata vs. control; # p < 0.05 for washout vs. E. ciliata of 0.3 µL/mL concentration; n = 7 for each).

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  Figure 4. Monitoring the use-dependence effect of the E. ciliata. (A,B) APs and (C,D) dV/dtmax response to abrupt change of the pacing cycle length from 400 ms to 200 ms in the control and after action of the E. ciliata (0.1 μL/mL), respectively. Arrows on the horizontal bar indicate the moment of the pacing cycle length switch. Notice a stronger reduction of dV/dtmax at an increased stimulation rate after application of the E. ciliata vs. control. For detection of the kinetics of dV/dtmax depression see Methods, (D, Insert) experimental points of dV/dtmax fitted with exponential decay (line) with τ = 0.55 s.

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  Figure 5. E. ciliata effects on optically recorded APs using voltage-sensitive fluorescent dye. Atrial/endo-/epi-cardial pacing with a 300 ms period was applied. (A–C) Superimposition of the optical APs (OAPs) and (D–F) their upstrokes on an expanded scale obtained in the control (CON; black) and after application of 0.01, 0.03, 0.1, and 0.3 μL/mL concentrations the E. ciliata (orange, grey, yellow and blue, respectively), followed by a washout period (WO; dotted). Notice a delay in activation time with 0.3 μL/mL concentration of the E. ciliata, and reversibility. Zero time indicates the time of stimulus.

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  Figure 6. Dependence of the OAP on the E. ciliata concentrations. Steady-state level measurements during atrial/endo-/epi-cardial stimulation (300 ms period) of (A) activation time, (B) voltage-sensitive fraction of fluorescence (ΔF/F), (C) OAP upstroke duration (UD), and (D) OAP duration (OAPD) at 20%, 50% and 90% of repolarization, done under the control (CON) conditions and at the end of each 10 min perfusion with 0.01, 0.03, and 0.1 µL/mL concentrations of the E. ciliata (except for 0.3 µL/mL the perfusion was ~5 min), followed by a washout (WO) period (* p < 0.05 for E. ciliata vs. control; # p < 0.05 for washout vs. E. ciliata of 0.3 µL/mL concentration; n = 6 for each).

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  Figure 7. Optical maps revealing E. ciliata effects on electrical activation process in the heart during epicardial stimulation. A voltage-sensitive fluorescent dye, di-4-ANBDQBS, was used. The pacing period was 300 ms. (A) Activation time (in ms), (B) conduction velocity (in m/s), and (C) conduction vector maps in the control and after applying 0.01, 0.03, 0.1, and 0.3 µL/mL concentrations of the E. ciliata, followed by a washout period. The interval between isochrones is 5 ms for the activation time, 0.1 m/s for the conduction velocity. Note that the conduction vector length is proportional to the conduction velocity. The direction of the activation wave movement is from blue-green to red. The stimulation electrode was located on the left close to the LV base.

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  Figure 8. Changes in OAP duration maps induced by E. ciliata during epicardial stimulation. (A) OAPD20, (B) OAPD50, and (C) OAPD90 maps in the control and after applying 0.01, 0.03, 0.1, and 0.3 µL/mL concentrations of the E. ciliata, followed by a washout period. OAPD20, OAPD50, and OAPD90 maps calculated at 20%, 50%, and 90% of repolarization, respectively. The interval between isochrones is 5 ms. Other notations are the same as in Figure 7.