Glial L-glutamate (L-Glu) transporter EAAT2 removes L-Glu at the synaptic cleft, thereby maintaining an efficient neurotransmission. Docosahexaenoic acid (DHA) is a major constituent of astrocyte membrane phospholipids and is released after L-Glu stimulation, however, the effects of DHA on L-Glu transporter have not been fully clarified. We studied the effects of DHA on EAAT2 electrophysiologically. Bath-applied DHA increased the amplitude of EAAT2 currents, but had no effects on EAAT1, another glial EAAT subtype. DHA has a negative charged carboxyl group that is deprotonated in a pH dependent manner. When the extracellular pH was decreased, the enhancement of EAAT2 by DHA was disappeared. No chargeable DHA analogue had no effects on EAAT2 currents, suggesting the negative charge is important. We identified which part of EAAT2 is important for the effects of DHA using EAAT1/2 chimeras. By substituting the transport domain of EAAT1 by that of EAAT2, the effects of DHA on EAAT1 were turned out to be enhancement, suggesting this region is important for the enhancement of EAAT2 current by DHA. Currently, we are identifying the essential region for the effect of DHA.