STABLE ANTICONVULSANT ACTION OF BENZODIAZEPINES DURING DEVELOPMENT INRATS

The anticonvulsant action of midazolam and clonazepam was studied in 1 68 immature rats in three age groups (12, 18 and 25 days old). Epilept ic after-discharges of the spike-and-wave type accompanied by clonic s eizures of facial and forelimb muscles induced by stimulation of senso rimotor cortex were used as a model. The solvent used for clonazepam e xhibited a tendency to anticonvulsant action in 12-day-old rats. On th e contrary. a proconvulsant action was seen in 25-day-old animals. The action of both benzodiazepines was identical and did not change subst antially during development. The highest dose used (1 mg kg-1, i.p.) s hortened the duration of epileptic after-discharges, the two lower dos es (0.1 and 0.02 mg kg-1, i.p.) suppressed the progressive prolongatio n with repeated stimulations seen under control conditions. Motor corr elates of stimulation remained practically uninfluenced by the two ben zodiazepines, myoclonic seizures accompanying epileptic after-discharg es were attenuated by the highest dose of both drugs.