A) An example of A1fB5r’s fluorescence changes upon depolarizations of 50 mV and 100 mV, and their recovery after the repolarization. The optical traces were smoothed with five passes of a binomial low pass filter. B) An example of incomplete fluorescent recovery after the repolarization. The optical trace was smoothed with a 60 Hz Gaussian low pass filter. Ten trials were averaged for both A and B. C) ΔF/F of A1fB5r versus membrane potential. The numbers of cells used for each data point: −50 mV: 10, −40 mV: 7, −30 mV: 4, −20 mV: 5, −10 mV: 16, 30 mV: 12. D) On time constant of A1fB5r versus holding potentials from −40 mV to 30 mV. The numbers of cells used for each data point: −40 mV: 5, −30 mV: 3, −20 mV: 5, −10 mV: 16, 30 mV: 12.