Figure 1. Excision of an outside-out patch reveals spontaneous non-selective cation channels.

A shows that excision of an outside-out patch between position (i) in whole-cell recording and (ii) excised outside-out patch reduces both holding current and ‘noise’. The rapid deflections in membrane current represent responses to a 10 mV hyperpolarising pulse. B shows the whole-cell current immediately prior to excision of the outside-out patch, (i) in A, and there was no distinctive single-channel activity. C illustrates that immediately after excision, (ii) in A, single inward ion channels (represented as downward deflections) were observed at the holding potential of -50 mV. D shows that the single ion channels displayed on a higher gain either opened for brief discrete periods of time (D) or displayed bursting characteristics (B). C, closed; O, open.