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We have studied the effects of the potassium-blocking agent 4-aminopyridine (4-AP) on the action potential and membrane currents of the sheep cardiac Purkinje fiber. 4-AP slowed the rate of phase 1 repolarization and shifted the plateau of the action potential to less negative potentials. In the presence of 4-AP, the substitution of sodium methylsulfate or(More)
The aim of the present study was to provide a mechanistic insight into how phosphatase activity influences calcium-activated chloride channels in rabbit pulmonary artery myocytes. Calcium-dependent Cl- currents (I(ClCa)) were evoked by pipette solutions containing concentrations between 20 and 1000 nM Ca2+ and the calcium and voltage dependence was(More)
1. Located within the gastrointestinal (GI) musculature are networks of cells known as interstitial cells of Cajal (ICC). ICC are associated with several functions including pacemaker activity that generates electrical slow waves and neurotransmission regulating GI motility. In this study we identified a voltage-dependent K(+) channel (Kv1.1) expressed in(More)
In order to learn about the endogenous Ca2+-buffering in the cytoplasm of chick dorsal root ganglion (DRG) neurons and the distance separating the ryanodine receptor Ca2+ release channels (RyRs) from the plasma membrane, we monitored the amplitude and time course of Ca2+-activated Cl- currents (I(ClCa)) in protocols that manipulated Ca2+-buffering.(More)
In voltage clamp studies of cardiac Purkinje fibers, a large early outward current is consistently observed during depolarizations to voltages more positive than -20 mV. After the outward peak of the current, the total membrane current declines slowly. Dudel et al. (1967. Pfluegers Arch. Eur. J. Physiol. 294:197--212) reduced the extracellular chloride(More)
We wrote a program that runs as a Microsoft Excel spreadsheet to calculate the diffusion of Ca2+ in a spherical cell in the presence of a fixed Ca2+ buffer and two diffusible Ca2+ buffers, one of which is considered to be a fluorescent Ca2+ indicator. We modeled Ca2+ diffusion during and after Ca2+ influx across the plasma membrane with parameters chosen to(More)
Epoxyeicosatrienoic acids (EETs) are arachidonic acid metabolites of cytochrome P450 monooxygenase, which are released from endothelial cells and dilate arteries. Dilation seems to be caused by activation of large-conductance Ca2+ activated K+ channels (BK(Ca)) leading to membrane hyperpolarization. Previous studies suggest that EETs activate BK(Ca)(More)
1. We used the patch-clamp technique to study voltage-activated transient potassium currents in freshly dispersed and cultured chick dorsal root ganglion (DRG) cells. Whole-cell and cell-attached patch currents were recorded under conditions appropriate for recording potassium currents. 2. In whole-cell experiments, 100-ms depolarizations from normal(More)
1. We used intracellular microelectrodes to record the membrane potential (Vm) of intact murine colonic smooth muscle. Electrical activity consisted of spike complexes separated by quiescent periods (Vm approximately -60 mV). The spike complexes consisted of about a dozen action potentials of approximately 30 mV amplitude. Tetraethylammonium (TEA, 1-10 mM)(More)
Recent whole-cell studies have shown that Ca(2+)-activated Cl- currents contribute to the Ca(2+)-dependent 4-aminopyridine-insensitive component of the transient outward current and to the arrhythmogenic transient inward current in rabbit and canine cardiac cells. These Cl(-)-sensitive currents are activated by Ca2+ release from the sarcoplasmic reticulum(More)