[Relationship between the magnitude of the inflowing current of isolated Limnea stagnalis mollusk neurons and the external concentration of the current-bearing calcium and strontium ions].

The dose-inward current relationships for current-carrying ions Ca2+ and Sr2+ were studied by means of intracellular dialysis and voltage clamp in isolated neurons of the mollusc Limnea stagnalis. For Ca2+ and Sr2+ ions these relationships had ceiling. The data obtained are explained in terms of activation theory using two-barrier model of calcium channel. Values of velocity constants vx for ion x2+ transition over the second energetic barrier and of constants Kx corresponding to effectiveness of binding in the channel's entrance were determined: vca:vsr = 1:2; KCa = 1400 M-1; KSr = 270 M-1.