Figure 9.

Concentration and voltage dependence of the parameters of the burst and slow blocked states. (A) The time constants of the exponentials that fit the burst duration (τ_b) (filled symbols) and long shut events (τ_l−s) (open symbols) (see Fig. 8) are plotted against [Sr²⁺]_i. (B) The ratio of the occurrence of the blocked state versus other shut states (n_1−s/n_s) is plotted against [Sr²⁺]_i. This fraction was calculated as the ratio of the area of the single-exponential component that fit long shut events (see Fig. 8, A–F, row b) to the total number of shut events counted. (C) Ratios of τ_b versus τ_l−s are plotted against membrane voltage. In A–C, different symbols indicate different membrane patches. More than two points obtained from the same membrane voltage in A and B or from the same [Sr²⁺]_i in C  are connected by dotted lines. Membrane voltage (in A and B) or [Sr²⁺]_i (in C) for each set of points are indicated. The slopes of the lines that fit each set of points: burst in A, −0.74 (30 mV, circle), −0.74 (50 mV, circle), −1.00 (square), −1.23 (10 mV, triangle), −0.78 (30 mV, triangle); slow blocked in A, −0.094 (30 mV, circle), and −0.11 (50 mV, circle), −0.05 (square), 0.01 (30 mV, triangle), −0.15 (10 mV, triangle); n _1−s/n _s in B, 0.92 (50 mV, circle) and 0.71 (30 mV, circle), 1.18 (square), 1.08 (30 mV, triangle), 0.95 (10 mV, triangle); τ_b/τ_l−s in C, log(e^−0.0381-fold) mV⁻¹ (circle, average), log(e^−0.0737-fold) mV⁻¹ (square), log(e^−0.0506-fold) mV⁻¹ (triangle, average).