EPILEPTIFORM ACTIVITY IN SEPTAL AND TEMPORAL HIPPOCAMPAL SLICES IN THE KAINATE MODEL OF TEMPORAL LOBE EPILEPSY
Abstract number :
2.081
Submission category :
Year :
2003
Submission ID :
575
Source :
www.aesnet.org
Presentation date :
12/6/2003 12:00:00 AM
Published date :
Dec 1, 2003, 06:00 AM
Authors :
Philip A. Williams, F. Edward Dudek Biomedical Sciences, Anatomy and Neurobiology Section, Colorado State University, Fort Collins, CO
In human temporal lobe epilepsy the anterior hippocampus is commonly identified as the focus or epileptogenic zone, and often surgical resection of this area can resolve or dramatically reduce the incidence of seizures. We hypothesized that in the kainate rat model of temporal lobe epilepsy, the temporal region would demonstrate more robust epileptiform activity as compared to the septal area.
Male Sprague-Dawley rats (200 gm) were treated with kainic acid (5 mg/kg, IP) hourly until motor seizures were induced. The animals were used for electrophysiologic experiments 6-12 mo after kainate treatment. Temporal and septal hippocampal slices were obtained from opposite hemispheres, and the slices were placed into the same interface chamber for extracellular recordings from the dentate gyrus with hilar stimulation (antidromic). After the recordings, the slices were processed for Timm staining.
In control solution, no slices were seen to produce all-or-none bursts of population spikes. Significantly more temporal slices produced all-or-none bursting than the septal slices when bathed in bicuculline and when the extracellular potassium was concurrently raised to 6 mM. When the extracellular potassium was raised to 8 mM, no difference in the proportion of slices with all-or-none bursting was found. The temporal slices also had significantly longer bursts of population spikes when compared to the septal slices for the different recording solution. The septal slices had a significantly higher threshold for bursting in 6 mM potassium. Timm stain of the recorded slices showed that the average score of Timm stain in the inner molecular layer of the temporal slices was significantly higher compared to the septal slices.
This finding may account for or contribute to the differences between the epileptiform responses of the temporal and septal hippocampus, although other extrinsic or intrinsic differences between the septal and ventral hippocampus could contribute to the disparity in the electrophysiologic responses.
[Supported by: NS16683.]