Abstracts

Rationale: Long-term activation of glia occurs in brain during epileptogenesis which develops after various CNS injuries. Since glia contributes to the production of proinflammatory molecules that play a key role in the onset and recurrence of seizures, we hypothesized that the extent and/or the duration of glia activation in crucial brain areas may be a predicitive marker of epilepsy development. We set up a MRS study to determine if glia activation can be imaged and quantified in vivo during epileptogenesis, since this technique detects changes in myo-inositol (m-Ins) and lactate (Lac) levels reflecting astrocytes and possibly microglia/macrophages activation, respectively. Methods: Status epilepticus (SE) was induced by pilocarpine in adult male rats. 1H-MRS measurements were performed in the hippocampus every 24 h for 7 d post-SE and in chronic epileptic rats, using a 7 Tesla Bruker Biospec. Spectra were processed and analysed using jMrui and TARQUIN freeware softwares. MRS results were validated in separate groups of rats by immunohistochemistry using astrocytes and microglia markers.Results: The quantitative analysis of MRS spectra showed a progressive increase in m-Ins levels from 24 h to 7 d post-SE vs control spectra: plateau levels were reached 7 d post-SE and were maintained in epileptic rats. Lac peak reached its maximum increase 48 h post-SE, progressively declining thereafter. These changes were confirmed by immunohistochemisty. Conclusions: MRS is a valuable in vivo technique for quantification of glia activation during epileptogenesis. Studies are in progress to determine if MRS measurements predict the development of epilepsy in rats.