Early hypoactivity of hippocampal rhythms during epileptogenesis after prolonged febrile seizures in freely-moving rats.

Prospective and experimental studies have shown that individuals with early-life complex/prolonged febrile seizures (FSs) have a high incidence of temporal lobe epilepsy during adulthood, revealing a close relationship between FSs and epilepsy. However, little is known about how epileptogenesis develops after FSs. The present study was designed to investigate acquired seizure susceptibility and analyze local field potentials during the latent period after FSs. We found that the seizure susceptibility decreased in 35-day-old (P35) FS rats but increased in P60 FS rats. Consistently, hippocampal electroencephalogram (EEG) power in every band was decreased at P35 but increased at P60 in FS rats. Our results provide direct evidence for hypoactivity but not hyperactivity during the early phase of the latent period, displaying a broad decrease in hippocampal rhythms. These characteristic EEG changes can be a useful biomarker for the early diagnosis of epileptogenesis induced by FSs.