Resumo

Objectives: Homer1a (Vesl-1S) is a protein that regulates metabotropic glutamate receptors type I (mGLuR1 and mGLuR5) in addition to being involved in a number of physiological processes and neuronal plasticity. It was recently demonstrated that Homer1a mRNA is enhanced after pilocarpine-induced status epilepticus. Here we investigated whether a single acute seizure triggered by means of maximal convulsive electroshock (MES) is able to alter Homer1a expression in the hippocampus. Methods: All experimental protocols were approved by the Universidade Federal de São Paulo Animal Care and Use Ethics Committee (0467/04). Electroshock-evoked seizures were induced in adult male Wistar rats (at 2 months, 200-250 g) using a stimulator and a current duration of 0.25 s (60 Hz, 150 mA). Subsequently animals were divided into ones that developed tonic-clonic seizures (MES+), did not develop tonic seizures (MES-) or controls (CTR) and analyzed at 2 (n=20), 8 (n=21), 24 (n=20) hours and 7days (n=22) after stimulation. Another group without any manipulation served as experimental control (baseline, BAL, n=5). Homer1a mRNA expression was analyzed by qPCR for hippocampal extracts. Results: qPCR of hippocampal extracts revealed Homer1a mRNA overexpression 2h after electroshock in MES- (0.80 ±0.12) and MES+ (2.12 ±0.14) as compared to BAL (0.05 ±0.01) and CTR (0.17 ±0.16) groups, additionally, MES+ has also a higher level of Homer1a than MES- group. The level of mGluR5 mRNA is diminished 24h after tonic-clonic seizures (0.53 ±0.21), when compared to BAL group (1.36 ±0.21), but mGluR1 mRNA content was unaltered by the all experimental procedures. Conclusion: The present data suggest that Homer1a mRNA expression level is related to the intensity of seizure, i.e. to the occurrence of tonic-clonic seizures. Our findings are consistent with the notion that overexpression of Homer1a in the hippocampus, may represent an intrinsic anticonvulsant or homeostatic mechanism.