Relationship between anticonvulsant activity and plasma level of some 2,3-benzodiazepines in genetically epilepsy-prone rats

The anticonvulsant effects of some novel 2,3-benzodiazepines acting as α-amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid/kainate (AMPA/KA) antagonists were evaluated in genetically epilepsy prone rats. The ED50 values against clonic and tonic seizures (in μmol/kg) revealed that the rank order of anticonvulsant activity was: GYKI 52466 > 2,3BZ-2 > 2,3 MBZ-2 > NBQX. Maximal anticonvulsant protection was observed 15-45 min after the IP administration of NBQX and GYKI 52466, 30-90 min after the IP administration of 2,3BZ-2, and 45-120 min after the IP administration of 2,3MBZ-2. The time course of plasma levels of rats treated with GYKI 52466 showed that peak plasma concentration was observed 15 min after IP administration, 2,3BZ-2 revealed that peak plasma concentration was achieved 45 min after IP administration, whereas following 2,3MBZ-2 administered IP, two curves were detected; one is referred to the parent compound and the other to its demethylate metabolite that corresponds to 2,3BZ-2. The therapeutic index (ratio of TD50 values for impaired rotarod performance and ED50 values for anticonvulsant activity) revealed that NBQX and GYKI 52466 were slighly more toxic than 2,3BZ-2 and 2,3MBZ-2. The present data suggest that 2,3-benzodiazepines acting at AMPA/kainate receptors play an important role in the generation and/or propagation of the audiogenic seizures in genetically epilepsy-prone rats. Copyright (C) 1998 Elsevier Science Inc.