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 Zn(2+)-mediated reduction of the low-threshold transient Ca(2+) current (I(T)) of a central element in thalamocortical oscillations. We found that Zn(2+) reversibly decreased I(T) in a concentration-dependent manner (IC(50)=55 microM), mainly by reducing the number of I(T) channels available for activation. Zn(2+) 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.