FIGURE 6.

Mutation of the Na2 site lowers apparent Li⁺ affinity but preserves DA binding. A, lithium dose-response curve for D420N (blue circles/solid line) compared with WT (black circles/dotted line). The currents were normalized to the maximum Li⁺ current and plotted against increasing Li⁺ concentrations. ChCl was isotonically substituted with LiCl. An EC₅₀ value could not be determined for D420N because no saturation was observed. B, I/V plot of steady-state leak currents in D420N in LiCl with and without perfusion of DA (100 μm) (means ± S.E., n = 5), showing that DA can bind to D420N.