[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. The shift along voltage axis of the inactivation curve for fast outward current under similar conditions was the same. At pH 9 the shift for a tenfold decrease in calcium concentration was 20 mV. Such an increase in the effect of calcium concentration change at pH 9 is probably due to the increase in the negative charge density in the vicinity of the potassium pathways. The dependence of the rate constants of inactivation alphab and betab for fast outward current upon the membrane potential was studied in solutions with different calcium concentration. The expressions for their calculation were obtained.