Abstract

Although simple febrile seizures are frequently described as harmless, there is evidence which suggests that hippocampal damage may occur after simple febrile seizures. This study aimed to investigate possible neuronal damages as well as alterations in cytogenesis in the hippocampal dentate gyrus following simple febrile seizures. Simple febrile seizure was modeled by hyperthermia-induced seizures in 22-day-old male rats. The brains were removed 2 or 15 days after hyperthermia in all rats with (n = 20) and without (n = 10) occurrence of seizures as well as in control animals (n = 10). The sections were stained with hematoxylin and eosin to estimate the surface numerical density of dark neurons. Ki-67 immunohistochemistry was performed to evaluate changes of cytogenesis following simple febrile seizures. Hyperthermia induced behavioral seizure activities in 67 of the rats. The numerical densities of dark neurons as well as the mean Ki-67 index (the fraction of Ki-67-positive cells) were significantly increased in dentate gyrus after induction of seizures by hyperthermia compared to both controls and rats without seizure after hyperthermia. Both the seizure duration and intensity were correlated significantly with numerical densities of dark neurons (but not with Ki-67 index). The data indicate that simple febrile seizures can cause neuronal damages and enhancement of cytogenesis in the hippocampal dentate gyrus, which were still visible for at least 2 weeks. These findings also suggest the correlation of febrile seizure intensity and duration with neuronal damage.