  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 $D(x) \propto
\exp(-\gamma x)$, $\gamma > 0$ 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, $f_c(t) \propto t^{-2 - \nu}$ for intermediate
times, where $\nu = U_c^{\prime}/\gamma \approx -0.3$ 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.
