Comparison Between Epileptic Activity and Granular Cell Dispersion in the Model of Intrahippocampal Injection of Kainate in Mice
Abstract number :
I.11
Submission category :
Year :
2000
Submission ID :
1715
Source :
www.aesnet.org
Presentation date :
12/2/2000 12:00:00 AM
Published date :
Dec 1, 2000, 06:00 AM
Authors :
Veronique Riban, Viviane Bouilleret, Bich Thuy Pham-Le, Fumio Suzuki, Christian Marescaux, Antoine Depaulis, INSERM U 398, Strasbourg, France; CEA, Orsay, France; Dept of neurosurgery and Anatomy, Shiga, Japan.
Rationale: Intrahippocampal injection of kainate in mice results in chronic recurrent focal seizures and histological modifications which are reminiscent of human Mesial Temporal Lobe Epilepsy. Following the initial status epilepticus, recurrent paroxystic discharges restricted to the injected hippocampus are EEG recorded concommitantly with behavioral arrest and/or stereotypies. In this model, hippocampal sclerosis develops in two phases: (i) within the first two weeks, cell loss is observed in the hilus and to a less extent in CA1, and (ii) after two weeks, an almost complete degeneration of CA1 is observed along whith a dispersion of granule cells in the dentate gyrus. The aim of this study was to determine whether the delayed granule cell dispersion influences the epileptic activity induced by intrahippocampal kainate in mice. Methods: Male swiss mice were stereotaxically injected with 1 nmol. of kainate in the right dorsal hippocampus. Cortical and depth electrode recordings were regularly performed on a digitized acquisition system. Nissl staining procedure was performed for histological studies. Results: Two groups of animals were distinguished based on EEG recordings : (i) In the first group, EEG activity was characterized during the first two weeks by a rythmic low voltage spikes activity occurring in sequence of short bursts. After 15 days, this paroxystic activity became organized in discharges characterized by a first train of high voltage sharp-waves followed by low voltage and high frequency spike-and-waves. Histological control of all these animals revealed a marked granule cell dispersion and an important cell loss in the hilus and CA1. (ii) In the second group, only low voltage spikes activity was recorded for up to 90 days. Cell loss in the hilus and CA1 was similar to the first group but no granule cell dispersion was observed in this group. Conclusion: In this model, a delay of two weeks is necessary for hippocampal paroxystic activity to be organized in focal epileptic seizures and these results suggest that granule cell dispersion is an important factor involved in this organization.