A low concentration of Cu²⁺ (13 nM) decelerates gating charge movement in Ca_v2.3. (A) Representative gating current traces (the average of 20 consecutive runs ± SD) recorded in response to the step depolarization to the reversal potential (V_r = 58 ± 2 mV; n = 8) in Tricine- (a and b) and Cu²⁺-containing (c) solutions (13 nM). (b and c) Enlarged view of the region selected with dashed lines on (a). (B) Maximal gating charges transferred across membrane in Tricine- and Cu²⁺-containing solutions (n = 7). (C) Amplitudes of the gating current transients recorded in Tricine- and Cu²⁺-containing solutions (*, P = 0.043, by paired Student’s t test; n = 7). (D) Time constants of the gating current transient decay measured in Tricine and Cu²⁺ solutions (*, P = 0.014, by paired Student’s t test; n = 7).