The quinoxaline derivative, 2,3-dihydroxy-6-nitro-7-sulfamoylbenzo (F) quinoxaline (NBQX), significantly reduced the currents evoked by exogenous application of quisqualate (QQ), kainate (KA) and alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) when applied to ganglion cells, using whole-cell recording in a slice preparation of the tiger salamander retina. A comparison between NBQX and CNQX indicates that NBQX is more effective in blocking AMPA receptors. Also, at up to 10 microM, NBQX has no effect on NMDA-induced currents. Thus at this concentration, NBQX shows no affinity for the glycine binding site of NMDA receptors. For this reason, NBQX is preferred over CNQX for a more effective and selective antagonism toward non-NMDA receptors.