Voltage and concentration dependence for Zn²⁺ effects on instantaneous (II-V) currents. (A) Voltage dependence of the logarithm of apparent dissociation constants (logK_Zn) for low-affinity Zn²⁺-induced suppression/block of II-V currents under the conditions indicated in B. Also shown in the middle are the voltage-independent logK_Zn values for the high-affinity component of II-V current suppression. Note the different scaling of the vertical axis. (B) Maximum suppression of II-V currents mediated by the high-affinity component. (C) Concentration dependence of II-V current suppression quantified in terms of the slope conductance between −40 and 20 mV (G_II-V).