The administration of ethanol (2 g/kg, i.p.) or of the non-competitive antagonist (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cycloepten-5,10-imine maleate (MK-801; 1 mg/kg, i.p.) induced a decrease in the extracellular concentrations of glutamate, as studied by microdialysis in the striatum of awake rats. Moreover, ethanol and MK-801 completely prevented the increase in extraneuronal glutamate concentration induced by the focal application of N-methyl-D-aspartate (NMDA). The present results suggest that ethanol suppresses glutamate release through an inhibition of NMDA glutamate receptors in the rat striatum.