Reliability of maximum number of simultaneously open channels as an estimator for the number of channels in single-channel recordings.

The single-channel recording technique has revolutionized the electrophysiological study of the ion channels. Interpretation of single-channel recordings often requires the exact number of channels present in a given patch--for example, derivation of the probability of a channel being open--and most theories handling gating kinetics assume that there is only one channel in the patch. Most investigators have estimated the number of channels as the number of maximal simultaneously open channels observed. Although this method is easy to understand and apply, examination of the validity of such estimation has not been much conducted before. As an attempt for such an examination, we have applied computer simulation method in order to obtain practically useful aids in judging the reliability of such estimates. Results show that (i) large estimated values (for example, larger than 10) are likely to be incorrect, and (ii) when the estimated value is small and the derived probability of a channel being open is within a certain range, the estimated number of channels is most likely to be correct.