Electrophysiological effects of GE 70 in isolated papillary muscle and ventricular myocytes of guinea pig hearts (part 6)

Effects on single channel current: The effect of 3 |J.mol/L GE 70 on single channel kinetics was studied in (S)-DPI 201-106 treated cell-attached patches (n=4). Figure 4 shows recordings from a typical experiment. The amplitude of the single channel current remained unchanged, while average open probability was reduced from 0.70±0.08 to 0.27±0.11 (P<0.05, n=4). The number of sweeps without activity was increased twofold by 3 |J.mol/L GE 70 from 15±5% nulls in control to 33±7% (n=4). Histograms of mean open and closed times (t) were best fitted with two exponentials. The mean open times were decreased (control: T1=3.9±0.5 ms, T2=38.3±4.7 ms; 3 |J.mol/L GE 70: T1=1.7±0.4 ms, P<0.05; T2=12.7±2.9 ms, P<0.05) and mean closed times were increased (control: T1=4.5±1.2 ms, T2=63.8±17.5 ms; 3 |J.mol/L GE 70: T1=5.5±1.6 ms, P>0.1; T2=154.7±22.3 ms, P<0.05) (Figure 5).

Electrophysiological effects of GE 70 in isolated papillary muscle and ventricular myocytes of guinea pig hearts

Figure 4 Eight consecutive sweeps of original recordings from a cell-attached patch containing one DPI-modified sodium channel (5 fimol/L (S)-DPI 201-106) are shown during control conditions (A) and in presence of3 fimol/L GE 70 (B) in the bathing solution. C,D The corresponding ensemble-averaged currents of202 sweeps each are shown. Depolarizing pulses of400 ms were applied from a holding potential of-100 mV to a test potential of-30 mV at a rate of 2 Hz. The mark at the beginning of each tracing indicates the baseline; downward deflections represent channel openings. The number of records without open channel activity was increased, and closed time between bursts was increased by GE 70

Electrophysiological effects of GE 70 in isolated papillary muscle and ventricular myocytes of guinea pig hearts

Figure 5 Histograms of mean open (left) and mean closed (right) times are shown during control conditions (A) and in presence of 3 fimol/L GE 70 (B) from the experiment illustrated in Figure 4. Mean open time was decreased by GE 70, while mean closed time was increased
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This entry was posted in Cardiology and tagged Action potential, Benzofuranylethanolamine, Cardiomyocytes, Papillary muscle, Propafenone, Sodium current.