Ontogenetic development of isonicotinehydrazide-induced seizures in rats

Motor seizures elicited by isonicotinehydrazide (INH) were studied in 188 male albino rats aged from 5 days to adulthood. INH was found to be able to induce both minimal, predominantly clonic, and major, i.e. generalized, tonic-clonic seizures during the whole course of development. Tonic hindlimb extension was observed as a part of major seizures even in the youngest group studied. Fifty-percent convulsant doses counted in 7-, 12-, 18-, 25- and 90-day-old rats did not significantly differ. The developmental changes found were a poor time resolution of minimal and major seizures during the first two postnatal weeks and significantly longer latency of major seizures in 5- and 7-day-old rat pups in comparison with all other age groups. The importance of the developmental stage of a generator of seizures as well as of the maturation of triggering mechanisms was demonstrated comparing the present results with our previous data.