The effects of brain-irradiation-induced decreases in hippocampal mitotic activity on flurothyl-induced epileptogenesis in adult C57BL/6J mice.
Previous studies have demonstrated that seizures are potent inducers of mitotic activity in the rodent hippocampus. The role of this mitotic activity in epileptogenesis currently remains unknown. In the present study, we investigated the effect of alterations in hippocampal mitotic activity on changes in seizure threshold and phenotype using flurothyl kindling. In flurothyl kindling, eight repeated flurothyl-induced generalized forebrain (clonic) seizures result in a rapid, progressive, and permanent lowering of the generalized seizure threshold in mice and in a slowly evolving increase in the percentage of animals expressing forebrain-brain stem (clonic-tonic) seizures when reexposed to flurothyl following a 2- to 4-week stimulation-free period. Therefore, flurothyl kindling serves as an excellent model for evaluating mechanisms of generalized seizure threshold and seizure propagation. To investigate this relationship between hippocampal mitotic activity and epileptogenesis, mice were given brain irradiation, focused mainly on the hippocampus, bilaterally, and were exposed to the flurothyl kindling model of epileptogenesis. Brain irradiation virtually eliminated all basal and seizure-induced mitotic activity in the hippocampal dentate gyrus of mice. In addition, animals that underwent irradiation and flurothyl kindling did not differ from control mice on measures of seizure threshold (threshold induction and maintenance) and seizure phenotype. Overall, these results suggest that seizure-induced increases in mitotic activity in the hippocampal dentate gyrus are not directly related to the processes that underlie the shift in behavioral seizure phenotype or in either the induction or the maintenance of lowered seizure threshold that is observed in this flurothyl model of epileptogenesis.
Ferland
Russell J
RJ
Graduate Program in Neuroscience, Strong Epilepsy Center, Department of Neurology, University of Rochester School of Medicine and Dentistry, 601 Elmwood Avenue, Rochester, NY 14642, USA.
Williams
Jacqueline P
JP
Gross
Robert A
RA
Applegate
Craig D
CD
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects / Q000528:radiation effects; D001921:Brain / Q000187:drug effects* / Q000473:pathology / Q000528:radiation effects*; D001973:Bromodeoxyuridine; D002452:Cell Count; D002455:Cell Division / Q000528:radiation effects; D003292:Convulsants; D018891:Dentate Gyrus / Q000187:drug effects / Q000473:pathology / Q000528:radiation effects; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004827:Epilepsy / Q000139:chemically induced* / Q000473:pathology; D005481:Flurothyl; D005720:Gamma Rays; D006624:Hippocampus / Q000187:drug effects / Q000473:pathology / Q000528:radiation effects; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008938:Mitosis / Q000528:radiation effects*
D003292:Convulsants; D005481:Flurothyl; D001973:Bromodeoxyuridine