Search results for "Cardiac transient outward potassium current"
showing 6 items of 6 documents
Inhibition by Fendiline of the Transient Outward Current in Rat Ventricular Cardiomyocytes
1999
The effects of fendiline on the transient outward current (Ito) were investigated in rat ventricular cardiomyocytes. Extracellularly applied fendiline reduced peak and steady-state current amplitude of Ito; the inactivation of Ito was accelerated by the drug, which reflects onset of block. The described effects were concentration dependent: half-maximal effects were achieved at approximately 3 microM fendiline. Intracellularly applied fendiline (3 microM) did not affect Ito within 5 min. The steady-state current amplitude of Ito was more efficiently suppressed by the drug at 22 +/- 1 degrees C than at 36 +/- 1 degrees C. The recovery of Ito was analyzed by the application of twin depolarizi…
Model predictions of the ionic mechanisms underlying the beating and bursting pacemaker characteristics of molluscan neurons
1976
The general properties of the excitable membrane on molluscan pacemaker neurons can be described on the basis of a fair amount of experimental evidence available in the literature. The neuronal membrane exhibits under voltage clamp an initial inward current carried by both Na+ and Ca2+ ions, the time- and voltage-dependent characteristics of which are similar to that of other excitable structures. The conductance mechanism for the two ion species and the transport kinetics appear to be closely similar. The time course and amplitude of the delayed outward current carried by K+ ions shows a marked dependence on the membrane potential. Characteristic for the molluscan neurons is the existence …
Different mechanisms of the inhibition of the transient outward current in rat ventricular myocytes.
1994
The mechanism of drug-induced inhibition of the transient outward current, Ito, has been investigated in rat ventricular myocytes using the whole cell patch clamp technique. Ito was activated by 300 ms depolarizing voltage clamp steps in 10 mV increments from −50 mV up to +40 mV. At +40 mV, Ito peaked after about 3 ms, and the time course of inactivation was appropriately described by two time constants, τfast = 17 ms and τslow = 203 ms. Verapamil, quinidine sulfate and nifedipine preferentially depressed Ito at the end of the 300 ms depolarizing voltage clamp step; the inactivation of Ito was accelerated by all drugs, whereas peak Ito was less affected. The time course of drug action at +4…
Mechanism of Block by 4-Aminopyridine of the Transient Outward Current in Rat Ventricular Cardiomyocytes
1998
The effects of 4-aminopyridine (4-AP) on the transient outward current (I to ) were investigated in rat ventricular cardiomyocytes at different values of intracellular pH (pH i ) and extracellular pH (pH o ). The 4-AP was administered either extracellularly (bath application) or intracellularly (diffusion from the intrapipette solution). The 4-AP diminished I to given either from inside or outside the cell membrane. The block by extracellularly applied 4-AP (4-AP o ) of the peak amplitude of I to was decreased by external acidification but increased by external alkalinization: conversely. the block by 4-AP o was decreased by internal alkalinization but increased by internal acidification. I…
Effects of Quinine and Quinidine on the Transient Outward and on the L-Type Ca<sup>2+</sup> Current in Rat Ventricular Cardiomyocytes
2002
The effects of the enantiomers quinine and quinidine on the transient outward current (I<sub>to</sub>) and on the L-type Ca<sup>2+</sup> current (I<sub>Ca</sub>) were investigated in rat ventricular cardiomyocytes using the patch-clamp technique. At a stimulation frequency of 2 Hz, both quinine and quinidine depressed the magnitude of I<sub>to</sub> and I<sub>Ca</sub>; the half-maximal effects on I<sub>to</sub> were achieved at 11 and 15 µmol/l, respectively, and those on I<sub>Ca</sub> at 14 and 10 µmol/l, respectively. At 0.2 Hz, both drugs depressed the magnitude of I<sub>to</sub>, but not tha…
Action of tertiary phenylalkylamines on cardiac transient outward current from outside the cell membrane.
1996
The effects of the phenylalkylamines verapamil (V), gallopamil (G), and devapamil (D) and their corresponding quaternary derivatives on the transient outward current (Ito) were examined in rat ventricular cardiomyocytes using the whole-cell patch-clamp technique. The question was addressed, whether phenylalkylamines act on Ito from the inside or the outside or from both sides of the cell membrane. To this end, the myocytes were either superfused extracellularly or perfused intracellularly with drug-containing solutions. In addition, the effects of verapamil were investigated at different pH-values. V, G, and D (30 microM each), applied extracellularly, reduced the steady state current of It…