Abstracts

In the Pilocarpine Model of Epilepsy (PME) the effects of Pilocarpine-induced [italic]status epilepticus [/italic](PSE) have been less studied in mice than in rats. We analyzed the temporal pattern of neuronal injury in the hippocampal formation of mice after the onset of PSE using Fluoro-Jade B (FJB) and Nissl stain. Sixty adult male Swiss (30-45 g) mice were used. Scopolamine methylnitrate (1 mg/Kg s.c.) was administered 30 min prior to pilocarpine. [italic]Status epilepticus[/italic] (SE) was induced by pilocarpine hydrochloride (340 mg/Kg i.p.). Controls groups received equivalents doses of NaCl 0.9 % instead of scopolamine methylnitrate and pilocarpine. The evolution of neuronal damage was quantified at 3 h, 6 h, 12 h, 24 h, one week and three weeks after the onset of the SE. Animals that exhibited uninterrupted seizures during 3 h from the onset of SE were included in the first time point group. In the other groups, only mice that had uninterrupted SE for at least 6 hours were included. FJB was used as a specific marker for neuronal degeneration. Adjacent sections were stained with cresyl violet for determine the distribution of the sections within the rostro-caudal axis and for assessment of the neuronal loss of the same regions evaluated by using of FJB. Fluoro-Jade B positive (FJB+) neurons count was performed in the CA1 and CA3 pyramidal cell layers and in the dentate gyrus (hilus and granular cell layer). The highest numbers of FJB+ neurons in CA1 and CA3 regions were found at 1 week after SE onset when compared with all the other times, showing differences statistically significant with regard to the group 3 h after onset of SE and to groups 3 h and 6 h after SE onset, respectively. In the hilus of the dentate gyrus, FJB+ neurons were found significantly higher 12 h after SE onset when compared to the 3 h and 3 weeks groups. In the granular cell layer of the dentate gyrus, there was no difference statistically significant between all SE groups. Control animals did not show Fluoro-Jade B staining in neurons of the same regions studied. The neuronal loss assessed by cresyl violet was scored on a 0-4 scale, by estimating in 25 % increments the number of healthy neurons remaining relative to control. The highest scores reached at the in CA1 and CA3 regions were at the groups 1 week, showing scores 1 and 4, respectively. In the hilus of the dentate gyrus, all the time points presented score 4. In the granular cell layer of the dentate gyrus all the groups show score 1, with the exception of the groups 3 h and 12 h after SE onset, with scores 0 and 0.5, respectively. This work provides evidences that the PME in mice is a reliable and reproducible model to study the physiopathological events underlying temporal lobe epilepsy. (Supported by CAPES and FAPESP.)