Effects of hyperthermia and continuous hippocampal stimulation on the immature and adult brain

Whether febrile seizures lead to hippocampal necrosis is a question of para mount clinical importance, This study attempted to simulate a complex febri le seizure, compared with hyperthermia (HYP) alone and prolonged seizure al one (produced by continuous hippocampal stimulation (CHS)), Four groups of rats were studied at each of two ages, immature (postnatal day, P20) and ad ult (P60). Group I was subjected to 45 min of HYP (body temperature 40 degr ees C) plus CHS, Group 2 received 45 min of HYP alone, Group 3 got 45 min o f CHS alone, and Group 4 was sham-handled control rats. Baseline and post-s ession EEGs were recorded in ail groups. Subsequently, brains were examined histologically for evidence of hippocampal damage. Both CHS-treated groups (with and without HYP) exhibited behavioral and EEG seizures while the gro up undergoing HYP alone did not have seizures. There were no gross histolog ical lesions in any group. Cell counts in regions CA1, CA3, dentate gyrus a nd dentate hilus did not differ in rats under any condition of hyperthermia and CHS, in either P20 or P60 rats compared to age-matched controls. These results indicate that both immature and mature rodents are resistant to hy perthermic brain damage and raises the question of whether febrile seizures play a role in the genesis of mesial temporal sclerosis. (C) 1999 Elsevier Science B.V. All rights reserved.