“The … alpha-aminoadipate … aspartate most strongly, glutamate and kainate moderately, and quisqualate only slightly; 2-amino-4-phosphonobutyrate antagonized N-methyl-D-aspartate most strongly, aspartate moderately … blocked kainate most strongly and others moderately; and kynurenate was rather nonselective but most strongly antagonized N-methyl-D-aspartate and aspartate.”