INCREASED SUSCEPTIBILITY TO TETANUS TOXIN-INDUCED SEIZURES IN IMMATURE RATS

Studies were undertaken to compare tetanus toxin-induced electrographi c and behavioral seizure activity in immature and adult rats. Multifoc al epileptiform activity was induced by unilateral hippocampal injecti on of tetanus toxin in 10-day-old immature and in 90-120-day-old adult rats. Bilateral cortical surface electrodes and, in some animals, hip pocampal depth electrodes were placed and serial video EEG was recorde d for 2 h during the week following tetanus toxin injection. Tetanus t oxin-induced interictal spike frequency was significantly higher and s eizure duration was significantly longer in immature compared to adult rats. Immature rats tended to have more frequent seizures compared wi th adults, but the difference was not statistically significant. Ictal behaviors were different for the two groups with immature rats common ly demonstrating wild running seizures which were not seen in adult ra ts. These findings suggest that there are age-dependent differences in electrographic and behavioral seizure expression in the tetanus toxin seizure model and that the epileptic syndrome in in immature rats is more severe. (C) 1997 Elsevier Science B.V.