ELECTROCONVULSIVE SEIZURES UP-REGULATE ASTROGLIAL GENE-EXPRESSION SELECTIVELY IN THE DENTATE GYRUS

Previous studies have revealed that kindled seizures induced via chron ically implanted electrodes up-regulate the expression of glial fibril lary acidic protein (GFAP), the protein constituent of intermediate fi laments in astrocytes. The present study evaluates the consequences of a single electroconvulsive seizure (ECS) on glial gene expression. EC S were induced in mice via externally-placed electrodes. GFAP mRNA lev els were evaluated 1, 2, 4, and 6 days post-seizure by in situ hybridi zation. GFA immunocytostaining was evaluated in a separate series of a nimals. Following a single ECS, the levels of mRNA for GFAP increased several fold by 1 day and were still substantially elevated at 4 days. The increases occurred primarily in the dentate gyrus despite the fac t that the seizures involved widespread brain regions. GFAP mRNA level s were also increased in areas bordering the ventricles, especially in areas immediately adjacent to the dentate gyrus. These results indica te that ECS up-regulates the mRNA for a key structural protein of astr ocytes in a manner that is similar to the response that occurs followi ng injury, that this response occurs selectively in a part of the brai n that plays a key role in memory function, and that the increase may be due in part to a diffusible substance that also affects glial gene expression in nearby structures.