Nonlinear drift-diffusion model of gating in the fast Cl channel

The dynamics of the open or closed state region of an ion channel may be described by a probability density p(x,t) which satisfies a Fokker-Planck equation. The closed state dwell-time distribution f(c)(t) derived from the Fokker-Planck equation with a nonlinear diffusion coefficient D(x)proportional to exp(-gamma x), gamma>0 and a linear ramp potential U-c(x), is in good agreement with experimental data and it may be shown analytically that if gamma is sufficiently large, f(c)(t)proportional to t(-2-nu) for intermediate times, where nu=U-c(')/gamma approximate to-0.3 for a fast Cl channel. The solution of a master equation which approximates the Fokker-Planck equation exhibits an oscillation superimposed on the power law trend and can account for an empirical rate-amplitude correlation that applies to several ion channels.