The effects of calibrated Zn²⁺ and Cu²⁺ concentrations on Ca_v2.3. (A, a) Representative current traces measured in response to a double-pulse protocol (depicted above) in Tricine- and copper-containing solutions. Copper concentrations at which currents were recorded are indicated in (b). (b and c) Time course of the effect of various Cu²⁺ concentrations on the amplitude of Ca²⁺ currents through Ca_v2.3, measured at −20 mV (b) and 20 mV (c). (B) Dose–response curves of the effect of Zn²⁺ and Cu²⁺ on gating of Ca_v2.3. Smooth lines represent the fit to the average data with the Hill equation (Zn²⁺: IC₅₀ = 1.3 ± 0.2 µM and n_H = 1.2; n = 6; and Cu²⁺: IC₅₀ = 18.2 ± 3.7 nM and n_H = 0.7; n = 8). (C) Dose–response curves of the effect of Zn²⁺ and Cu²⁺ on conductance of Ca_v2.3. Smooth lines represent the fit to the average data with the Hill equation (Zn²⁺: IC₅₀ = 8.1 ± 1.4 µM and n_H = 0.60; n = 6; and Cu²⁺: IC₅₀ = 269 ± 101 nM and n_H = 0.5; n = 8). (D and E) Voltage dependence of activation (D) and steady-state inactivation curves (E), measured in Tricine solution and solutions containing either 8 µM Zn²⁺ or 293 nM Cu²⁺. Data were fitted with a Boltzmann equation (Table 1).