alpha-Amino-3-hydroxy-5-methyl-isoxazole-4-propionate/kainate (AMPA/kainate) receptor antagonists (at subthreshold doses against electroconvulsions), 1-(4-aminophenyl)-4-methyl-7,8-methylenedioxy-5H-2,3-benzodiazepine (GYKI 52466 at maximally 5 mg/kg) and 2,3-dihydroxy-6-nitro-7-sulfamoylbenzo(F)quinoxaline (NBQX at maximally 20 mg/kg) enhanced the protective effects of NMDA receptor antagonists, MK-801 (dizocilpine) or 2-(2-carboxypiperazine-4-yl)-1-propenyl-1-phosphonic acid (D-CPP-ene), against electroconvulsions. Similarly, MK-801 or D-CPP-ene reduced the ED50 values of both NBQX and GYKI 52466 against maximal electroshock. The adverse effects of D-CPP-ene, evaluated in the chimney and rotorod tests, were potentiated by both GYKI 52466 (2.5 mg/kg) and NBQX (10 mg/kg). Also, D-CPP-ene (0.1 mg/kg) worsened the motor performance of mice pretreated with GYKI 52466 in the rotorod test. Neither MK-801 (0.025 mg/kg) nor D-CPP-ene (0.1 mg/kg) affected the NBQX-induced impairment of motor coordination. Similarly, GYKI 52466 (2.5 mg/kg) or NBQX (10 mg/kg) did not influence the performance of mice treated with MK-801 (0.2 mg/kg). It may be concluded that the blockade of more than one subtype of glutamate receptors leads to a more pronounced anticonvulsive effect when compared with the effect of blockade of an individual receptor subtype. In some cases more efficient seizure protection was not associated with increased adverse effects.