The anticonvulsant effects of 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(f)quinoxaline (NBQX), phencyclidine (PCP) and diazepam against audiogenic seizures in DBA/2 mice and against seizures induced by methyl-6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate (DMCM) in NMRI mice were compared. Motor impairment was assessed in a rotarod apparatus in DBA/2 as well as NMRI mice. At 30 min after i.p. administration, NBQX was as effective as PCP and diazepam in protecting against audiogenic seizures and had a therapeutic ratio slightly higher than diazepam's and 7-fold higher than PCP's. Whereas diazepam was fully effective, NBQX and PCP were both ineffective against seizures induced by DMCM 30 min after i.p. administration. The anticonvulsant potential and motor-impairing effects of NBQX were evaluated further by the i.p. and the i.v. routes at different time points after administration. At all pretreatment intervals, NBQX protected against audiogenic seizures more potently than it produced motor impairment. NBQX administered i.p. protected against DMCM-induced seizures when given 15 min but not 5 min before testing, whereas after i.v. administration NBQX produced anticonvulsant and motor-impairing effects in the same dose range. NBQX only slightly and non-dose-dependently attenuated the discriminative effects of pentylenetetrazole in rats, showing a limited anxiolytic potential. NBQX produced no PCP-like or morphine-like discriminative effects in rats, suggesting lack of PCP or opiate-like subjective effects. These data demonstrate that NBQX has anticonvulsant effects, has limited anxiolytic effects, and does not produce subjective effects of PCP or opiate type.