Abstracts

To describe distribution of status epilepticus[ndash]induced neuronal degeneration in the selected neocortical and transitional cortical areas in 25[ndash]day[ndash]old rats. Time course of changes was studied to find out possible differences at various survival intervals. Specific attention was given to laminar distribution of degenerated cells. Experiments were carried out in Wistar rat pups 25 days old. Lithium[ndash]pilocarpine model of SE was used. Lithium chloride (3 mmol/kg, i.p.) was injected 24 hours before pilocarpine (40 mg/kg, i.p.). Only animals exhibiting convulsive status epilepticus (SE) were included in this study. The rats survived for 4, 8, 12, 24, 48 hours and/or 1 week after SE. Four to five animals were processed in each survival interval. The animals were perfused with phosphate[ndash]buffered saline (PBS) followed by 4% paraformaldehyde in PBS under an overdose of urethane anesthesia. Coronal sections (40 [mu]m thick) were cut on a cryostat, mounted onto gelatine[ndash]coated slides, and processed with cresyl violet or with a fluorescent stain Fluoro-Jade B (FJB) used for detection of degenerated neurons in different cortical areas (motor, somatosensory, cingular, agranular insular, ectorhinal, perirhinal and retrosplenial areas). Sections were examined with an epifluorescence microscope using a filter system suitable for visualizing fluorescein or fluorescein isothiocyanate (FITC). A small to moderate number of FJB[ndash]positive neurons was found 4, 8 and 12 hours after SE in transitional cortical areas (cingular, agranular insular, perirhinal, ectorhinal area) as well as in the motor area. These neurons were distributed in supragranular as well as in infragranular layers. In contrast, degenerated neurons prevailed in infragranular layers of the retrospenial area and the somatosensory area. Majority of FJB[ndash]positive neurons were small to medium sized cells with round or spindle-shaped nonpyramidal perikarya. Basic differences between transitional cortical areas and motor cortex remained unchanged at longer survival intervals (24 and 48 hours) but the number of FJB-positive neurons significantly increased. In addition, pyramidal neurons were markedly represented among degenerated elements at these intervals. One week after SE degenerated neurons persisted in all analyzed areas but their number was reduced in comparison with preceding intervals. Lithium[ndash]pilocarpine model of SE resulted in degeneration of neurons in transitional as well as in sensorimotor cortical areas in 25[ndash]day[ndash]old rats evident at all survival intervals. At shorter intervals majority of degenerated cells exhibited features of local interneurons whereas pyramidal neurons represented a substantial part of FJB-positive cells 24 hours after SE and later. Individual cortical areas exhibited characteristic laminar pattern in distribution of degenerated neurons. (Supported by grants No.304/04/0464 and 309/03/0770 of the Grant Agency of the Czech Republic.)