Abstracts

Rationale: Experimental data indicate alteration of hypothalamic functions in animals after severe seizures. It is in agreement with clinical findings in some patients; in many cases their epilepsy started in infancy or early childhood. Therefore we decided to study presence and time course of possible neuronal degeneration induced in hypothalamus of immature rats by status epilepticus. Methods: Experiments were carried out in Wistar rat pups 12, 15, 18, 21 and 25 days old. SE was induced by pilocarpine (40 mg/kg, i.p.) 24 hours after lithium chloride (3mmol/kg,i.p.) pretreatment. Paraldehyde (0.07-0.3 ml/kg according to age) was administered to interrupt seizures after two hours of continuous convulsions. Control siblings received saline instead of pilocarpine. The rats survived for 4, 8, 12, 24, 48 hours or 1 week after SE. Four to five animals were processed in each survival interval. The animals were perfused with 4 % paraformaldehyde under an overdose of urethane anesthesia. Every fifth coronal section (50 ?m thick) was stained with Fluoro-Jade B (FJB) for detection of degenerating neurons (Schmued and Hopkins 2000), subsequent sections were stained with cresyl violet for differentiation of individual hypothalamic nuclei. Labelled cells were plotted and transferred to standard stereotaxic sections (Paxinos and Watson 2007). Results: Only isolated degenerating neurons were observed in 12- and 15-day-old animals mainly in the posterior hypothalamus. Since the postnatal day 18 degenerating neurons were distributed in several hypothalamic nuclei. FJB-positive neurons were consistently found in the anterior hypothalamic area, in the ventromedial nucleus, in tuberal area and in the highest number in the mammillary complex. Within the mammillary complex marked neuronal damage was evident in premammillary and supramammillary nuclei. Besides these nuclei, dispersed FJB-positive neurons occured in the lateral hypothalamic area. Animals with SE at the age of 18 and more days exhibited neuronal damage at all survival intervals with a peak at 24 and 48 h after SE. One week after SE persisted degenerating neurons only in the supramammilary nuclei. Conclusions: Lithium-pilocarpine SE elicited in immature rats led to neuronal degeneration also in the hypothalamus. Consistent neuronal damage was found if SE was induced in 18-day-old and older animals. FJB-positive neurons were found at all survival intervals with a maximum at 24 and 48 h after SE. The degenerating neurons prevailed in the posterior hypothalamic region namely in the mammillary complex. Paxinos G., Watson C.: The rat brain in stereotaxic coordinates. Academic Press, 2007. Schmued L.C., Hopkins K.J.: Toxicol. Pathol. 28: 91-99, 2000. This study was supported by grant No. 304 /07 /1137 of the Grant Agency of the Czech Republic and by a project LC554.