How powerful is the dwell-time analysis of multichannel records?

Abstract

Exact algorithms for the kinetic analysis of multichannel patch-clamp records require hours to days for a single record. Thus, it may be reasonable to use a fast but less accurate method for the analysis of all data sets and to use the results for a reanalysis of some selected records with more sophisticated approaches. For the first run, the tools of single-channel analysis were used for the evaluation of the single-channel rate constants from multichannel dwell-time histograms. This could be achieved by presenting an ensemble of single channels by a "macrochannel" comprising all possible states of the ensemble of channels. Equations for the calculations of the elements of the macrochannel transition matrix and for the steady-state concentrations for individual states are given. Simulations of multichannel records with 1 to 8 channels with two closed and one open states and with 2 channels with two open and two closed states were done in order to investigate under which conditions the one-dimensional dwell-time analysis itself already provides reliable results. Distributions of the evaluated single-channel rate constants show that a bias of the estimations of the single-channel rate constants of 10 to 20% has to be accepted. The comparison of simulations with signal-to-noise ratios of SNR = 1 or SNR = 25 demonstrates that the major problem is not the convergence of the fitting routine, but failures of the level detector algorithm which creates the dwell-times distributions from noisy time series. The macrochannel presentation allows the incorporation of constraints like channel interaction. The evaluation of simulated 4-channel records in which the rate-constant of opening increased by 20% per already open channel could reveal the interaction factor.