Biophysical Journal
Volume 77, Issue 2, August 1999, Pages 701-713
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M-Channel Gating and Simulation

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Abstract

Single potassium M-channels in rat sympathetic neurons have multiple voltage-dependent kinetic components in their activity: short, medium, and long closed times (τCS, τCM, and τCL) and short and long open times (τOS and τOL). All five components can be detected in cell-attached patches, but only four of them (τCS, τCM, τOS, and τOL) in excised patches (Selyanko and Brown, 1993, J. Physiol. (Lond.). 472:711–724; 1996, Neuron. 16:151–162; 1996, Neuropharmacology. 35:933–947). Analysis of the burst structure of activity recorded from cell-attached and excised inside-out patches showed it to be consistent with the sequential kinetic scheme CL  OS  CM  OL  CS. Using this scheme and experimentally determined kinetic parameters, we successfully simulated the activity of M-channels both under steady-state conditions and during depolarizing voltage steps. Consistent with the characteristic behavior of macroscopic M-current, ensemble currents constructed from simulated M-channels had exponential activation and deactivation, with no delays, when tested in the range between −50 and −20 mV.

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