Effects of Zn²⁺ on Ca_v2.3 channel voltage dependence. (A–C) Families of mean current traces carried by 4 mM free Ca²⁺ and recorded with the protocols depicted above in the absence (black) and presence (orange) of 5.4 µM free Zn²⁺ at pH 7.4 (n = 5 cells in A and C, and 6 cells in B). Scale bar corresponds to 5 ms and 20 pA/pF in A, 5 ms and 50 pA/pF in B, or 10 ms and 200 pA/pF in C. (D) I-V relationships determined with the protocol in A before (black squares), during (orange circles), and after (gray diamonds) application of 5.4 µM free Zn²⁺ (same cells as in A). (E) II-V relationships determined with the protocol in C before (black squares), during (orange circles), and after (gray diamonds) application of 5.4 µM free Zn²⁺ (same cells as in C). (F) Isochronous activation (right) and PPI (left) curves determined from tail currents recorded with the protocol in A or peak currents recorded with the protocol in B, respectively, before (open squares), during (orange circles), and after (gray squares) application of 5.4 µM free Zn²⁺ (same cells as in A and B). (G) Boxplots comparing the Zn²⁺-induced shifts in half-activation voltage (V_0.5act), half-inactivation voltage (V_0.5inact), and apparent V_rev. (H) Boxplots comparing the Zn²⁺-induced changes in activation slope factor (k_act) and inactivation slope factor (k_inact). *, P < 0.05; ***, P < 0.001 (one-way repeated-measures ANOVA).