FIGURE 4. Current-voltage (I-V) relationships of Ca_V1.2e1b and Ca_V1.2e1c channels when expressed with auxiliary subunits.

Ba₂⁺ currents were normalized to facilitate comparison. A, I-V relationships of Ca_V1.2e1b and Ca_V1.2e1c when co-expressed with α₂δ. B, steady-state inactivation of Ca_V1.2e1c and Ca_V1.2e1b currents when co-expressed with α₂δ. Exemplar current traces of 1-s conditioning depolarizing pulses evoked at −80, +10, and +30 mV followed by 200-ms test pulses to 0 mV (left panel). Cell capacitances for original recordings were: Ca_V1.2e1c + α₂δ, 90 pF; Ca_V1.2e1b + α₂δ, 66 pF. Mean steady-state inactivation fit with a Boltzmann function (right panel). C, voltage-dependent activation of Ca_V1.2e1c and Ca_V1.2e1b currents when co-expressed with α₂δ. Exemplar tail currents evoked by repolarization to −80 mV after depolarizing test pulses to −20, 0, 20, and 40 mV (left panel). Cell capacitances for original recordings were: Ca_V1.2e1c + α₂δ, 98 pF; Ca_V1.2e1b + α₂δ, 66 pF. Mean voltage-dependent current activation (right panel). D, inactivation of Ca_V1.2e1b/α₂δ and Ca_V1.2e1c/α₂δ currents were best fit with a single exponential function. Tau was similar for Ca_V1.2e1b/α₂δ and Ca_V1.2e1c/α₂δ currents.