[³H]CFT binding potency of modafinil and other DAT ligands in the absence of extracellular Na⁺ and the effect of Zn²⁺ on binding affinity.

Assays were performed in Na+-free conditions (buffer sodium was isotonically replaced with the impermeant cation NMDG+) in the presence and absence of 10 micromolar zinc; values are means ± SEM for 3–7 experiments, each performed in triplicate. *Significant difference versus Na+-Free affinity value (p<0.05; t test, two-tailed).