Resumo

Aims: The regulation of many genes and proteins is altered in models of temporal lobe epilepsy, leading to modifications in the neuronal systems involved in the epileptogenesis process. Homer1a is an immediate early gene (IEG) product that binds to metabotropic glutamatergic receptors (mGluR1 and mGluR5). Homer1a expression is increased as a consequence neuronal hyperexcitability. Methods: All experimental protocols were approved by the Universidade Federal de São Paulo Animal Care and Use Ethics Committee (0467/04). Rats weighing 200-250mg (n=4 per group) received pilocarpine injections (320mg/Kg, i.p.) preceded by methyl-scopolamine (1mg/kg, i.p.). The animals were evaluated according to established times after SE, generating the experimental groups: 30min, 1h, 2h, 8h, 24h and 7d. The control groups are: Basal animals, without any manipulation (naïve), and the Saline group, that received saline solution rather than pilocarpine (Sal). Homer1a, mGluR1 and mGluR5 tRNA expression were analyzed by qPCR of hippocampal extracts. Homer1a, mGluR1 and mGluR5 protein expression were analyzed by western blotting analysis of hippocampal total protein extract, and their anatomical distribution were determined by immunohistochemestry tests. Results: tRNA analysis shows that of Homer1a has the highest expression at 2 (0.63 ± 0.05) and 8 (0.97 ± 0.05) hours after SE as compared to NSE (0.09 ± 0.04), Saline (0.05 ± 0.09) and naïve (0.05 ± 0.01) groups. The tRNA of mGluR5 shows a decrease at 24 hours after SE (0.16 ± 0.14) when compared to naïve group (1.36 ± 0.21). Homer1a protein expression increased at 30 minutes (5.91%) and 8 hours after SE (8.97%) when compared to saline group. The histological data demonstrated that Homer1a acutely increased in animals undergoing status epilepticus (SE) mainly at CA1 and dentate gyrus of hippocampus. Conclusions: Our results suggest that pilocarpine SE induction is able to increase Homer1a and down-regulate mGluR5 expression. We suggest this increase of Homer1a might be regulating mGluR5 and thus consequently regulating hyperexcitability. Financial support: FAPESP (Brazil)