Abstracts

Rationale: Temporal Lobe Epilepsy (TLE) is the most common type of epilepsy. In general around one third of all epilepsies are classified as TLE, which usually settles after an initial insult. After a latent period, when neuroplastic alteration occurs, the spontaneous recurrent seizures (SRSs) emerge. To better study the plastic mechanisms involved in epileptogenenesis, we used the animal model of electrical stimulation of the amygdala to induce self-sustained status epilepticus (SSSE). Our aims were to evaluate circuitry activation, neurodegeneration and neurogenesis processes and their possible relationship with the behavior during the SSSE. Methods: Adult male Wistar rats were implanted with electrodes in the left amygdaloid complex (AmyC) and hippocampal formation (HF). Video-EEG was recorded. AmyC was electrically stimulated for 30 min and the animals developed SSSE for 1.5 h, after what they received 5 mg/kg diazepam. Rats were perfused after 3 h (n = 7 SE; 4 controls), 24 h (n = 7 SE; 3 controls) and 14 days (n = 8 SE; 5 controls). Control animals were implanted but were not stimulated. Brain slices were stained for Fos and Ki-67 (3 h group), FluoroJade (FJ) and Ki-67 (24 h group) and Doublecourtin (DCX) (14 days group). Analyzed areas were neocortex, entorhinal cortex, pyriform cortex, AmyC and HF. For the analyses of Fos and FJ each area was classified according to the relative number of stained cells based on an arbitrary scale validated by three blinded observers to the animal's group. For the analyses of cell proliferation (Ki-67) and neurogenesis (DCX), each stained cell in the dentate gyrus was counted in 4 slices. All experiments were conducted according to Ethics on Animal Experimentation. Results: The rats were divided based on the behavioral pattern during SSSE: type I with most severe seizures (limb myoclonus, falling, running and jumping) and type II with less severe seizures (facial automatisms and neck myoclonus). Epileptiform EEG was recorded in AmyC and HF channels and was qualitatively similar for both types of SSSE. None of the control rats presented behavior or EEG alterations. There was a stronger Fos staining in the SE type I in neocortex (p<0.05) and amygdala (p<0.001). There was a strong neurodegeneration in all analyzed areas, and FJ staining was significantly higher in HF of SE type I than in SE type II (p<0.05). SE type II presented mostly unilateral neurodegeneration in all analyzed areas (p<0.001). Both group of SE animals (Type I and II) show a significant increase in the number of Ki-67 cells at 3 h (P<0.05) and 24 h (P<0.001) and DCX was also increased at 14 days (P<0.001) in both HF. Conclusions: This study shows that behavioral expression of SE is associated to specific circuitry activation (Fos) and neurodegeneration (FJ) patterns. Widespread activation and neurodegeneration are seen in SE type I and they are more restrict in SE type II. However, cell proliferation (Ki-67) and neurogenesis (DCX) were equally increased in both types of SSSE in contrast with control animals. Supported by FAPESP, PROEX-CAPES, CNPq.