Calcium potentiation demonstrated in the outside-out patch configuration. Top: Continuous recording of current as a function of time from an outside-out patch containing wild-type α7 nAChRs at a holding potential of −70 mV and bandwidth of 7 kHz. Gray bars indicate perfusion with a solution containing 10 µM ACh and 1.8 mM Ca²⁺, whereas black bars indicate perfusion with 10 µM ACh without calcium. Bottom: The durations of individual channel openings are plotted as a function of time of occurrence during the recording.