Abstracts

Rationale: The septum (septum verum) is a prominent telencephalic structure, anatomically and functionally heterogenous which operates in the transmission of signals from the brain stem to the hippocampus and other cortical areas. The glutamatergic projections from the hippocampus and subiculum dominate among the afferent connections of the lateral septum. The efferent connections arise mainly in the medial septal region and terminate in all fields of the hippocampus. The prominent part of the septohippocampal projection is cholinergic. Experimental data about neuronal damage within the septum after status epilepticus (SE) are sparse and only adult animals were analyzed. Systematic study and developmental data about neuronal damage of the septum in immature animals after SE are missing. Methods: Experiments were carried out in male Wistar rat pups 12, 15, 18, 21 and 25 days old. Lithium-pilocarpine model of SE was used. Lithium chloride (3 mmol/kg i.p.) was injected 24 hours before pilocarpine (40 mg/kg, i.p.). Control animals were treated with LiCl and saline. Only animals exhibiting convulsive status epilepticus (SE) were included in this study. The rats survived for 4, 8, 12, 24, 48 hours and 1 week after SE. Four to five animals were processed in each survival interval. The animals were perfused under an overdose of urethane anesthesia with PBS followed by 4% paraformaldehyde in PBS. Coronal sections (40 μm thick) were processed with cresyl violet or with a fluorescent stain Fluoro-Jade B (FJB) used for detection of degenerated neurons. Sections were examined microscopically with an epifluorescence microscope using a filter system suitable for visualizing fluorescein or FITC. Results: No or only isolated degenerated neurons were found mainly in the lateral region of 12-day-old and 15-day-old rat pups. In 18-day-old and older pups degenerated neurons were distributed in lateral septal region with prevalence to intermediate a ventral nucleus and to posterior half of the region. Since P18 neuronal damage was found in all survival intervals and reached peak at 24 and 48 h after SE. No FJB-positive cells were present in medial septal region in all age categories and survival intervals. Moderate to large number of degenerated neurons was evident in the bed nucleus of the stria terminalis. Conclusions: Lithium-pilocarpine model of SE in immature rats resulted in degeneration of neurons in the lateral septal region with prevalence in its posterior half. Consistent neuronal damage was found in 18-day-old and older animals. Damage increased with survival interval and reached peak at 24 and 48 h after SE. No degenerating neurons were found in the medial septal region. This study was supported by Projects No. P304/12/G069 of the Grant Agency and No. ME08045 and LH11015 of the Ministry of Education of the Czech Republic.