Cultured microglia expresses AMPA (α-amino-hydroxy-5-methyl-isoxazole-4-propionate)-type of glutamate (Glu) receptors but its functional importance has not been cleared yet.Here we examined the functional change of AMPA receptors before and after microglial activation by lipopolysaccaride (LPS).Using the conventional whole-cell patch clamp technique under the voltage-clamp condition, Glu-induced currents were observed in the presence of cyclothiazide (CTZ), an inhibitor of AMPA receptor desensitization.After stimulation of microglia with LPS, Glu-induced inward currents were inhibited time-dependently while the expression of GluR2, which is critical subunit determining Ca2+ permeability, was up-regulated, in accordance with a previous report that homomeric receptor channels composed of the edited form of GluR2 produce no appreciable current responses.