Abstracts

Rationale: Nucleus accumbens septi (NAS) is a prominent part of ventral striatum. NAS is heterogenous structure divided into ventromedial shell and dorsolateral core compartments. The core region has been referred as the motor sector of NAS, while the shell region is considered to be associated with motivation behaviors. In an effort to better understand the development of neuronal damage in the striatopallidal complex after status epilepticus (SE) in developing brain neuronal degeneration was analyzed within both compartments of the NAS.Methods: Experiments were carried out in Wistar rat pups 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.). Only animals exhibiting convulsive status epilepticus (SE) were included in this study. The rats were left to survive 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 cut on a cryocut, mounted onto gelatine-coated slides, and processed with cresyl violet or with a fluorescent stain Fluoro - Jade B (FJB) used for detection of degenerated neurons. Sections were examined with an epifluorescence microscope using a filter system suitable for visualizing fluorescein or FITC. Results: A small to moderate number of FJB – positive (degenerated) neurons was found 4, 8 and 12 hours after SE in the NAS. These neurons were distributed in the shell compartment of the NAS. At survival interval 24 hours the number of degenerated neurons in the shell subdivision of the NAS significantly increased and FJB – positive neurons were evident in the whole anteroposterior and mediolateral extent of the nucleus. At longer survival intervals 48 hours and 1 week after SE degenerated neurons persisted in the shell subdivision of the NAS but their number was reduced in comparison with 24-hour interval. The core region contained isolated degenerated neurons only in interval 4 h after SE. There were no FJB – positive neurons at any interval in the ventral pallidum.Conclusions: Lithium–pilocarpine model of SE led to degeneration of neurons not only in the dorsal striatum (as demonstrated previously) but in the same survival intervals after SE also in the ventral striatum. In all survival intervals degenerated neurons were evident only in the shell subdivision of the NAS. Degenerating neurons were rare in the core subdivision only immediately after SE and absent in the ventral pallidum at all survival intervals. Supported by grant No. 304/07/1137 of the Grant Agency of the Czech Republic.