A–C, original recordings of 1-s depolarizing pulses to −80, −20, −10, and 0 mV followed by 200-ms test pulses to 0 mV for each subunit combination indicated. D–F, voltage dependence of steady-state inactivation for each subunit combination. G–I, voltage dependence of inactivation constants for each combination specified. Inactivation of CaV1.2/α2δ/β1b and CaV1.2/α2δ/β3 currents were best fit with a bi-exponential function representing τfast and τslow, whereas CaV1.2/α2δ/β2a current inactivation was best fit with a single exponential. * illustrates p < 0.05.