FIGURE 3.

Transient PC2 currents are greater with slower Ca²⁺ buffering (0.25 mM EGTA compared to 0.25 mM BAPTA). (A) The recordings shown were made with 0.25 mM EGTA (left) or 0.25 mM BAPTA (right) at +20 mV immediately following prepulses of 10 s to the voltages shown. Postpulse currents are shown and were measured in the same cilium. This cilium had multiple active PC2 channels, preventing resolution of single-channel events. (B) In a cilium with just one PC2 channel, transient currents were also activated by prepulses of 10 s to the voltages shown. The postpulse voltage was +40 mV and the buffer was 0.25 mM EGTA. (C) The effect of slower Ca²⁺ buffering is reversible. A cilium showed transient currents in 0.25 mM EGTA before and after exposure to 0.25 mM BAPTA, in which transient currents were not seen. Prepulse and postpulse voltages were −80 mV and +60 mV, respectively. (D) Paired transient current amplitudes for 11 cilia, each tested in both 0.25 mM EGTA and 0.25 mM BAPTA. Voltages were chosen that gave the greatest transient current in 0.25 mM EGTA. Prepulse voltages ranged from −140 to −60 mV and postpulse voltages from +20 to +80 mV. For a given cilium, the same pair of voltages was used in both EGTA and BAPTA. *p < 0.001. (E) Histogram showing the most positive prepulse voltage sufficient to cause a transient current in 0.25 mM EGTA in each of 16 cilia.