The big deal about single-channel information

What can single-channel records tell us about gating? The purpose of this chapter is to illustrate how single-channel records can distinguish between very different gating mechanisms that nevertheless demonstrate similar behavior at the level of macroscopic currents (the level studied by Hodgkin and Huxley (HH)). To exploit the new gating information contained in single-channel records, we need to think about channels in a new way: as a special class of stochastic process, a Markov process. We will only develop a bare-bones primer on Markov processes, just enough to understand a case example taken from the annals of Na channel gating: Aldrich RW, Corey DP, and Stevens CF (1983), ‘A reinterpretation of mammalian sodium channel gating based on single-channel recording.’ Nature 306 436–41. This initial foray into single-channel analysis will motivate a more complete treatment of Markov process analysis of ion channel gating in subsequent chapters.