Electrophysiological effects of GE 70 in isolated papillary muscle and ventricular myocytes of guinea pig hearts (part 3)

guinea pig hearts (part 3)

Single channel recording: Single ventricular myocytes were enzymatically dissociated . Experiments were performed at room temperature (22±1°C). A bathing solution was used containing (in mmol/L) potassium aspartate 140, MgCl2 2, EGTA 10, ATP 2 and HEPES 10, titrated with KOH to pH 7.4. Cells were depolarized by this extracellular solution to about 0 mV. The pipette solution contained (in mmol/L) NaCl 140, HEPES 10, CsCl 10, MgCl2 2 and CaCl2 1.8, titrated with NaOH to pH 7.4. Single channel currents were measured in the cell-attached mode of the patch clamp technique .Borosilicate pipettes (Corning, World Precision Instruments) with a resistance of about 5 to 10 MQ were coated with Sylgard (Dow Corning, Seneffe, Belgium). Depolarizing steps of 20 ms were delivered from holding potentials between -140 and -70 mV to a test potential of -30 mV by a pulse generator at a frequency of 2 Hz. The same pulse protocol was used during the control period and in the presence of the drug. Voltage-dependence of peak sodium current was studied by applying 20 ms depolarizing pulses from a holding potential of-120 mV to test potentials ranging from -70 to +60 mV. In some experiments, 5 |J.mol/L (S)-DPI 201-106 (Sandoz, Basel, Switzerland) was added to the bathing solution in order to slow fast inactivation of the sodium current. In these experiments depolarizing pulses of 400 ms duration were applied. The currents were filtered at 5 kHz with a Kemo Variable Filter VBF/8 (Kemo Limited, Beckenham, Kent, United Kingdom), and digitized using an ana-logue-to-digital converter (TL-1, Axon Instruments, Foster City, California, USA), which was connected with a personal computer.
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This entry was posted in Cardiology and tagged Action potential, Benzofuranylethanolamine, Cardiomyocytes, Papillary muscle, Propafenone, Sodium current.