| dc.description.abstract | Ion channels open and close in a stochastic fashion, following the laws of
probability. However, distinct from tossing a coin or a die, the probability of
finding the channel closed or open is not a fixed number but can be modified
(i.e., we can cheat) by some external stimulus, such as the voltage. Single-channel
records can be obtained using the appropriate electrophysiological technique (e.g.,
patch clamp), and from these records the open probability and the channel conductance can be calculated. Gathering these parameters from a membrane containing
many channels is not straightforward, as the macroscopic current I iNPo, where i
is the single-channel current, N the number of channels, and Po the probability of
finding the channel open, cannot be split into its individual components. In this
tutorial, using the probabilistic nature of ion channels, we discuss in detail how i, N,
and Po max (the maximum open probability) can be obtained using fluctuation
(nonstationary noise) analysis (Sigworth FJ. G Gen Physiol 307: 97–129, 1980). We
also analyze the sources of possible artifacts in the determination of i and N, such as
channel rundown, inadequate filtering, and limited resolution of digital data acquisition by use of a simulation computer program (available at www.cecs.cl). | |
