Figure 4. β-subunit-dependent run-down of Cav2.3 channel Ca²⁺ current in tsA-201 cells.

Data for Cav2.3 co-expressed with α2δ1 and β2a (orange) or β3 (green) are shown. (A). Run-down during a 0.1 Hz square pulse protocol (20 ms to V_max, holding potential –89 mV). Currents were normalized to the I_Ca of the sweep with the maximal peak inward current observed during the recording. After a full block with 100 µM Cd²⁺ currents recovered to the amplitude preceding the Cd²⁺ application. (B) Cells were held at –89 mV and then stimulated using the regular SN DA neuron pacemaking protocol for 30 s, 1 min, and 2 min each followed by 20 s long pauses (vertical dashed lines) at hyperpolarized potentials (–89 mV) to allow channel recovery from inactivation. I_AP of individual APs was normalized to the inward current of the first AP. The current run-down component can be estimated from the non-recovering current component (horizontal dashed lines). Traces represent means ± SEM from the indicated number of experiments (N=2). BS, bath solution.