Zinc reduces low-threshold Ca²⁺ currents of rat thalamic relay neurons

Whole-cell voltage-clamping of thalamic relay neurons was used to examine the possibility of a Zn²⁺-mediated reduction of the low-threshold transient Ca²⁺ current (I_T) of a central element in thalamocortical oscillations. We found that Zn²⁺ reversibly decreased I_T in a concentration-dependent manner (IC₅₀=55 μM), mainly by reducing the number of I_T channels available for activation. Zn²⁺ did not affect the reaction kinetics, but did affect the voltage-dependence of I_T channel gating. However, the apparent alterations in gating properties were not enough to account for the huge I_T reduction.