UNIVERSAL STEADY-STATE I-V RELATIONSHIP FOR MEMBRANE CURRENT

A purely electrical mechanism for the gating of membrane ionic channel gives rise to a simple I-V relationship for membrane current, Our app roach is based on the known presence of gating charge, which is an est ablished property of the membrane channel gating, The gating charge is systematically treated as a polarization of the channel protein which varies with the external electric field and modifies the effective po tential through which the ions migrate in the channel, Two polarizatio n effects have been considered: 1) the up or down shift of the whole p otential function, and 2) the change in the effective electric field i nside the channel which is due to familiar effect of the effective red uction of the electric field inside a dielectric body because of the p resence of surface charges on its surface, Both effects are linear in the channel polarization, The ionic current is described by a steady s tate solution of the Nernst-Planck equation with the potential directl y controlled by the gating charge system, The solution describes reaso nably well the steady state and peak-current I-V relationships for dif ferent channels, and when applied adiabatically, explains the time lag between the gating charge current and the rise of the ionic current, The approach developed can be useful as an effective way to model the ionic currents in axons, cardiac cells and other excitable tissues.