FIGURE 1.

Transient PC2 currents are greater with reduced internal Ca²⁺ buffering (0.1 mM BAPTA compared to 2 mM BAPTA). (A) The recordings shown were made with 0.1 mM BAPTA (left) or 2 mM BAPTA (right) at +60 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. In this and other recordings, the dashed line represents the current when all PC2 channels were closed. (B) In a cilium with just one active PC2 channel, the channel was also activated by prepulses of 10 s to the voltages shown, and again only at the lower concentration of BAPTA. The postpulse voltage was +60 mV. (C) The effect of reduced Ca²⁺ buffering is reversible. A cilium with a single PC2 channel showed transient currents in 0.1 mM BAPTA before and after exposure to 2 mM BAPTA, in which transient currents were not seen. Prepulse and postpulse voltages were −70 mV and +40 mV, respectively. (D) Paired transient current amplitudes for 15 cilia, each tested in both 0.1 and 2 mM BAPTA. Voltages were chosen that gave the greatest transient current in 0.1 mM BAPTA. Prepulse voltages ranged from −140 mV to −40 mV and postpulse voltages from +40 mV to +80 mV. For a given cilium, the same pair of voltages was used in both 0.1 and 2 mM BAPTA. *p < 0.001. (E) Histogram showing the most positive prepulse voltage sufficient to cause a transient current in 0.1 mM BAPTA in each of 17 cilia.