Figure 1.

Copper and zinc block GABA mediated currents. (A) illustrates the block of currents evoked by sequential application of 2 μM GABA+0, 3, 10, 30, 100 μM Zn²⁺ in the absence of Cu²⁺ in the bath solution. (B) shows results from another cell to which the same set of solutions was applied, however in the presence of 100 nM Cu²⁺ in the bath solution. Applications were made every 30 s and are marked by thin lines (GABA) and hatched bars (Zn²⁺). The response following trace 5 (coapplication of GABA and 100 μM Zn²⁺) displays still a partial removal of Cu²⁺-block by the preceding Zn²⁺-application. (C) In Cu²⁺-free bath solution Zn²⁺ blocks GABA mediated currents in a concentration-dependent manner (open circles). Data points are fitted in equation 1 with I_max=0.66±0.05, IC₅₀=36±5 μM; n=1±02. In the presence of 100 nM Cu²⁺ the concentration-response curve is biphasic (filled circles). Data points are normalized to the response elicited by 2 μM GABA in Cu²⁺-free solution. Each data point averages the responses of six cells.