Two non-steroidal anti-inflammatory drugs, niflumic acid and diclofenac, inhibit the human glutamate transporter EAAT1 through different mechanisms.

We investigated the effects of non-steroidal anti-inflammatory drugs on substrate-induced currents of L-glutamate (L-Glu) transporter EAAT1 expressed in Xenopus laevis oocytes. Niflumic acid (NFA) and diclofenac inhibited L-Glu-induced current through EAAT1 in a non-competitive manner. NFA produced a leftward shift in reversal potential (E(rev)) of L-Glu-induced current and increased current amplitude at the potentials more negative than -100 mV. Diclofenac had no effects on E(rev) and inhibited the current amplitude to the same extent at all negative potentials. These results indicate that NFA and diclofenac inhibit the L-Glu-induced EAAT1 current via different mechanisms.