[Hydrogen currents through aconitine-modified sodium channels in nerve fiber membranes].
Ionic currents in nodal membrane treated with aconitine were measured under voltage clamp conditions when nodes were bathed in Na-free solutions. At pH lower than 4.6 inward ionic currents were detected which had kinetics and voltage range of activation analogous to those of aconitine-modified sodium channels at low pH. These currents were blocked by benzocaine (2 mM). Experiments with various concentrations of Ca2+, tris+, TEA+, choline+ ions showed that these ions are essentially impermeable both at normal and acidic pH. It is concluded that the inward currents observed are carried by H+ (or H3O+) ions through aconitine-modified sodium channels. From reversal potential measurements relative permeability (PH/PNa) of sodium channels is estimated to be 1059 +/- 88. The results suggest that the aconitine-modified channel is a rather wide water-filled pore and the rate of H+ passing through the channel is limited by its binding to an acidic group.
D000157:Aconitine / Q000494:pharmacology*; D031841:Aconitum / Q000031:analogs & derivatives*; D000818:Animals; D001566:Benzocaine / Q000494:pharmacology; D006859:Hydrogen / Q000378:metabolism*; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects*; D007700:Kinetics; D008564:Membrane Potentials; D009413:Nerve Fibers, Myelinated / Q000187:drug effects*; D009431:Neural Conduction; D011895:Rana ridibunda; D012964:Sodium / Q000378:metabolism*
D007473:Ion Channels; D006859:Hydrogen; D012964:Sodium; D001566:Benzocaine; D000157:Aconitine
Vodorodnye toki cherez modifitsirovannye akonitinom natrievye kanaly v membrane nervnogo volokna.