FIGURE 8.

(A) Whole-cell current-voltage relationship in the presence of 5 mM divalent (same as Fig. 1 B) and I/V voltage protocol (inset). (B) The whole-cell current-voltage relationship in the presence of 60 mM Ca²⁺ (solid squares) and Ba²⁺ (open circles). The data are displayed as mean ± SE normalized to the peak current in Ca²⁺. In the cases where the error bars are not visible, it is because they are smaller than the size of the symbol. For whole-cell experiments, the bath solution was the same as the single-channel pipette solution containing 60 mM Ca²⁺ and 60 mM Ba²⁺, respectively. (C) Average whole-cell open-channel I/V relationship in 5 mM Ca²⁺ (solid squares) and 5 mM Ba²⁺ (open circles) and voltage protocol (inset). The data are displayed as mean ± SE normalized to the current in Ca²⁺ at −80 mV. In the cases where the error bars are not visible, it is because they are smaller than the size of the symbol. The half-solid circles are the Ba²⁺ data shifted 10 mV positive (as described in text). Data were filtered at 100 kHz by an 8-pole low-pass Bessel filter and digitized at 200 kHz. Currents were recorded at hyperpolarized potentials after depolarization to +60 mV for 1 ms. (Inset) Capacity- and leak-corrected representative currents in 5 mM Ba²⁺ (upper) and Ca²⁺ (lower). Traces were filtered offline to 20 kHz and the first 0.05 ms are not shown. (D) Average whole-cell open-channel I/V relationship in 60 mM Ca²⁺ (solid squares) and 60 mM Ba²⁺ (open circles). The data are displayed as the mean ± SE normalized to the Ca²⁺ at −80 mV. In the cases where the error bars are not visible, it is because they are smaller than the size of the symbol. The half-solid circles are the Ba²⁺ data shifted by 20 mV (as described in text). Currents were recorded at hyperpolarized potentials after a brief depolarization to +115 mV for 1 ms. Data were filtered at 100 kHz by an 8-pole low-pass Bessel filter and digitized at 200 kHz. (Inset) Capacity- and leak-corrected representative currents in 60 mM Ba²⁺ (upper) and Ca²⁺ (lower). Traces were filtered offline to 20 kHz and the first 0.06 ms are not shown.