Abstracts

Rationale: Temporal Lobe Epilepsy (TLE) is the most common epileptic syndrome in humans. Status Epilepticus (SE), one of the primary events leading to TLE, induces neuronal loss and neurogenesis. Several studies in TLE detected alterations of subpopulations of GABAergic interneurons that express calcium-binding proteins (CaBPs). Therefore, in the present study we evaluated the expression of CaBPs, in two experimental models of TLE induced by pilocarpine (PILO). Methods: Adult male Wistar rats (250-300 g; Control, n=16; PILO, n=25) were submitted to systemic (S-PILO) and intrahippocampal (H-PILO) (1 day of survival). Fluoro-Jade+ (FJ+), Caspase 3+ neurons, in H-PILO (1, 7 and 15 days of survival) were counted. S-PILO (320 mg/kg; 2 ml/kg, i.p); H-PILO (2.4 mg/µL [CaBPs]/1.2 mg/µL) Parvalbumin+ (PV+)/Calretinin+(CR+) neurons were counted in the dentate gyrus (DG), Ammon's Horn subfields (CA1, CA2 and CA3) and in cerebral cortex, doublecortin+ (DCX+) neurogenesis was evaluated 15 days after SE. Results: In the S-PILO model PV+ neurons increased in CA1 (p<0.05), CA3 (p<0.01) and cortical layers V-VI (p<0.01). In the H-PILO model we observed significant PV+ expression in GD (p<0.05), CA2 (p<0.01), CA3 (p<0.01) and in cortical layers V-VI (p<0.01). In the H-PILO model we found no changes in CR+ cells, while in the S-PILO model, we found increases in GD (p<0.01), CA1 (p<0.05), CA3 (p<0.01) and cortical subregions II-III (p<0.05) and V-VI (p<0.005). FJ+ neurons were increased in hilus/CA3(P<0,05) 1 day after SE when compared to other time windows and in CA1(p<0.01) 7 days after SE when compared with other areas. Caspase 3+ cells increased in hilus (p<0.0001) when compared with controls. DCX+ cells increased in GD 15 days after SE (p<0.0001) when compared to controls. Conclusions: These data indicate that in these two experimental models of TLE specific hippocampal and cortical regions are the most affected in terms of neurodegeneration/ neurogenesis processes, coupled to a differential spatial response of subpopulations of PV+ and CR+ interneurons. Support: FAPESP, FAPESP-Cinapce, CNPq-PROSUL, CAPES and FAEPA.