  We present a new approach to nicotinic receptor kinetics and a new model
explaining random variabilities in the duration of open events. The model gives
new interpretation on brief and long receptor openings and predicts (for two
identical binding sites) the presence of three components in the open time
distribution: two brief and a long. We also present the physical model of the
receptor block. This picture naturally and universally explains receptor
desensitization, the phenomenon of central importance in cellular signaling.
The model is based on single-channel experiments concerning the effects of
hydrocortisone (HC) on the kinetics of control wild-type (WT) and mutated
alphaD200Q mouse nicotinic acetylcholine receptors (nAChRs), expressed in HEK
293 cells. The appendix contains an original result from probability renewal
theory: a derivation of the probability distribution function for the duration
of a process performed by two independent servers.
