Signal function of potassium channels--clinical aspects.

Potassium (K+) channels are the most diverse class of ion channels, and are important for regulating neuronal excitability and signaling activity in a variety of ways. They are major determinants of membrane excitability, influencing the resting potential of membranes, wave forms and frequencies of action potentials, and thresholds of excitation. Voltage-gated K+ cannels exist not as independent units merely responding to changes in transmembrane potential but as macromolecular complexes able to integrate a plethora of cellular signals that fine tune channel activities.

[Modulation of voltage-gated sodium channels by recombinant interferon-alpha2b in the human neuroblastoma cell line IMR-32].

Clonal human neuroblastoma cells imr-32 are a suitable model system for studies of neuronal excitability modulation. The ability interferon-alpha 2b "laferon" to modulate the mechanisms of electrical activity was studied in whole-cell patch-clamped undifferentiated human neuroblastoma cells IMR-32. It was shown that 1 h incubation of IMR-32 cells at 37 degrees C in medium with laferon (600 U/ml) exerted changes in voltage-dependent properties of Na(+)-channels.

Effects of temperature and Na0+ on the relaxation of phasic and tonic tension of guinea-pig ureter muscle.

Effects of temperature and Na0+ on the relaxation of guinea-pig ureter smooth muscle were studied. Relaxation of phasic contraction was found to be highly temperature-dependent, practically independent of Na0+ and Ca02+, and resistant to vanadate. The relaxation of the tonic tension of both high-K and low-Na contracture was less temperature-dependent and affected by Na0+.

Effects of caffeine on the electrical and mechanical activity of guinea-pig ureter smooth muscle.

The effects of caffeine on the electrical and mechanical activity of the guinea-pig ureter smooth muscle were studied. Under untreated conditions caffeine mainly showed inhibitory action on the ureter, inhibiting the evoked action potentials and phasic contractions as well as potassium contracture. Caffeine was also found to suppress the low-Na contracture of Na-loaded ureter muscle.

The effects of local anaesthetics on the electrical and mechanical activity of the guinea-pig ureter.

The effects of local anaesthetic tertiary amines (procaine, lignocaine and tetracaine) as well as neutral (benzocaine) and permanently charged (QX-314) local anaesthetics were studied on the evoked electrical and mechanical activity of the ureter smooth muscle. 'Low' concentrations of procaine and lignocaine (0.1-1mM) at pH 7.

[Electroregulated potassium channels of the somatic membrane of mollusk neuron membranes].

The delayed potassium current in mollusc neurons was separated into two components: a noninactivating component and a transient (inactivating) component. A noninactivating potassium current is not affected by changes in temperature, whereas an inactivating component decreases substantially under cooling. Internal Na+ can block the delayed outward potassium current.

[Thermodynamic characteristics of the gating mechanisms of fast potassium channels of somatic membranes of snail neurons].

The fast potassium current conductance was treated as a system obeying n3 kinetics. The steady-state arrangement of the gating charges have been analyzed in terms of a Boltzmann distribution with two allowed configurations. Rate equations were obtained using the transition rate theory and assuming that each reaction was rate limited by only one energy barrier.

[Effect of the alkaloid lappaconitine on ion currents through the somatic membrane of Helix pomatia neurons].

The effect of alkoloid lappaconitine on ionic currents through the somatic membrane of identified neurons of the mollusc Helix pomatia was studied under voltage-clamp conditions. It is shown that 4 mM lappaconitine causes a reversible blocking action on the calcium channels. Concentration exceeding 4 mM causes irreversible changes.

[Quantitative description of a slowly inactivating barium current through the somatic membrane of mollusk neurons].

The slow-inactivating barium current was recorded under voltage clamp conditions from identified neurons of the snail Helix pomatia. Experimental data were analyzed using the Hodgkin-Huxley equations. The dependence of the steady-state value of the inactivation variable on membrane potential was obtained.

[Mechanisms of prolonged action potential generation in barium solutions].

The membrane currents were recorded under voltage clamp from identified nerve cells of the Helix pomatia. The replacement of the external Ca ions in normal solution by Ba ions produced a shift in the potassium conduction-voltage curve along the voltage axis in the positive direction. The decrease in the limiting value of the potassium conduction was also observed.

[Effect of calcium ions on potential-dependent potassium channels in the membrane of the soma of giant mollusc neurons].

The delayed and fast outward currents in the somatic membrane of mollusc giant neurons were studied under voltage-clamp conditions in normal (10 mM) and low-Ca (I mM) saline. At pH 7.2 a tenfold decrease in calcium concentration in the peak conductance vs membrane potential curves for delayed and fast outward currents were shifted along the voltage axis by 10 mV.