We determined the effects of the N-methyl-D-aspartate (NMDA) receptor
blocker MK-801 (0.05, 0.1, and 0.5 mg/kg intraperitoneally, i.p.) and
phenytoin (PHT, 5, 10, and 20 mg/kg i.p.) on flurothyl-induced clonic
and tonic-clonic seizures in 9-, 15-, 30-, and 60-day-old male rats. B
oth agents had seizure-, age-, and dose-specific effects. The highest
dose of MK-801 was anticonvulsant against clonic flurothyl-induced sei
zures only in 9- and 60-day-old rats, but suppressed tonic-clonic seiz
ures in all ages. The lowest dose of MK-801 (0.05 mg/kg) produced sign
ificant anticonvulsant effects only in 15 day old rats. PHT did not ha
ve any effect on clonic seizures throughout development. Both doses of
PHT (10 and 20 mg/kg) were anticonvulsant against tonic-clonic seizur
es in adult rats but not in any other age group. The results indicate
that NMDA receptors play an important role in tonic-clonic flurothyl-i
nduced seizures throughout development (especially in 15-day-old rats)
and that the anticonvulsant effects of PHT may vary at different stag
es of brain development.