Graded Ca2+ release evoked by voltage-clamp pulses. (A) Voltage-clamp pulses for 50 ms were applied from a holding potential of −50 mV to various depolarized levels, from −38 to +30 mV, in increments of 2 mV. All recordings in all panels except for (D) are plotted with gradient colors from blue to red, coded in reference to the test potentials shown in (A). (B) Whole-cell ICaL. (C) [Ca2+]blk. (D) The voltage relationship of peak ICaL (red) and peak d[Ca2+]blk/dt (blue) was recorded with test pulses in 2 mV increments, normalized by each peak value. (E) Time evolution of Yooo, Ycco, Yoco, and Ycoo. (F) Ca2+ accumulation in jnc is represented by Ca00.