Stochastic behaviour of ion channels in varying conditions

The opening and closing of a single ion channel can be describedas the aggregation into two sets of states, open and shut, ofan underlying Markov process with a finite number of states.In this paper we consider an inhomogeneous process due to changingphysical conditions, in particular a pulse of activity in whichthe transition rates during the pulse differ from those obtainingboth before and after the pulse. Outside the pulse the chaincontains an absorbing shut subset, so that no activity is observedbefore the pulse and, almost surely, at most a finite numberof openings are generated by the pulse. We consider, in particular,the probability distribution of first latency (the time to firstopening) and the distribution of the total activation time.We take into account the phenomenon of time-interval omission,when short open or shut times fail to be observed.