Figure 6. Effects of external Ca²⁺ on inward currents in ICC.

In A peak currents were recorded repetitively by stepping cells from −100 mV to −60 mV every 30 s (pipette solution III; E_Cl= 0 mV). External CaPSS was replaced with Ca²⁺-free (0-Ca²⁺) solution (black bar). Reduction in external Ca²⁺ caused inhibition of inward current, and this effect was reversible upon restoration of CaPSS. B, representative traces (a–d) before, during and after removal of Ca²⁺ at time points indicated in A. C, peak currents were recorded by stepping repetitively from −80 mV to −50 mV every 30 s. External Ca²⁺ (CaPSS) was replaced with equimolar Ba²⁺ (2 mm; BaPSS; black bar). Peak currents were inhibited by BaPSS, and this effect was reversible when CaPSS was restored. Representative traces from the time points indicated in C are shown in D (a–d). E, peak currents were recorded by stepping repetitively from −80 mV to −35 mV every 30 s. Ni²⁺ (30 μm, black bar) added to the CaPSS inhibited the inward current. The effects of Ni²⁺ were slow to wash out. Representative traces from the time points indicated in E are shown in F (a–d).