DL-TBOA ammonium is a potent non-transportable inhibitor of?excitatory amino acid transporters?with?IC50s of 70 μM, 6 μM and 6 μM for?excitatory amino acid transporter-1 (EAAT1),?EAAT2?and?EAAT3, respectively. DL-TBOA ammonium inhibits the uptake of [14C]glutamate in COS-1 cells expressing the human?EAAT1?and?EAAT2?with?Ki?valuesof 42 μM and 5.7 μM, respectively. DL-TBOA ammonium blocks?EAAT4?and?EAAT5?in a competitive manner with?Ki?values of 4.4 μM and 3.2 μM, respectively