Excitatory amino acid antagonists, lamotrigine and BW 1003C87 as anticonvulsants in the genetically epilepsy-prone rat.

Sound-induced seizures in genetically epilepsy-prone rats were used to compare the anticonvulsant effect of phenytoin and diazepam with compounds which decrease glutamatergic neurotransmission including excitatory amino acid antagonists acting at N-methyl-D-aspartate (NMDA) receptors: D(-)CPPene, CGP 37849 and MK 801 or at the glycine/NMDA site: ACPC (1-aminocyclopropane-dicarboxylic acid) (partial agonist) or non-NMDA receptors: NBQX (2,3-dihydroxy-6-nitro-7-sulfamoylbenzo[f]-quinoxaline.Li) and GYKI 52466 (1-(aminophenyl)-4-methyl-7,8-methylene-dioxy-5H-2,3-benzodiazepin e.HCl) or acting at sodium channels to decrease glutamate release: lamotrigine and BW 1003C87 (5(2,3,5-trichlorophenyl)-2,4-diaminopyrimidine ethane sulphonate). ED50 values against clonic seizures (in mumol/kg at the time of peak anticonvulsant effect) were: phenytoin 30.5 (2 h), diazepam 0.5 (0.5 h), MK 801 0.01 (4 h), D(-)CPPene 1.9 (4 h), CGP 37849 2 (1 h), GYKI 52466 24 (0.25 h), NBQX 40 (0.5 h), ACPC 1053 (0.5 h), BW 1003C87 2.2 (1 h), lamotrigine 4.8 (4 h). BW 1003C87, lamotrigine, MK 801, phenytoin, diazepam and CGP 37849 had the most favourable therapeutic indices (rotarod locomotor deficit ED50/anticonvulsant ED50).