TRANSCRIPTOMIC ANALYSIS OF HIPPOCAMPAL SUBREGIONS AFTER INDUCTION OF ACUTE SEIZURES BY ELECTRIC STIMULATION OF THE PERFORANT PATHWAY IN RATS

Preconditioning is a mechanism in which injuries induced by non-lethal hypoxia or seizures trigger cellular resistance to subsequent events. Norwood et al., in a 2010 study, showed that an 8-hour-long period of electrical stimulation of the perforant pathway in rats is required for the induction of hippocampal sclerosis. However, in order to avoid generalized seizures, status epilepticus (SE), and death, a state of resistance to seizures must be induced in the hippocampus by a preconditioning paradigm consisting of 2 daily 30-minute stimulation periods. The present study aims to investigate differential gene expression patterns in different hippocampal subregions using RNA- sequencing, after induction of a preconditioning protocol by electrical stimulation of the perforant pathway. The dorsal and ventral dentate gyrus (dDG, vDG), CA3 (dCA3, vCA3) and subiculum (dSub, vSub) regions were collected by laser-microdissection 24 hours after preconditioning protocol induction in rats. RNA sequencing was performed in a Hiseq 4000 platform, reads were aligned using the STAR and DESEq2 statistics package was used to estimate gene expression. When comparing control to preconditioned samples, we found the differential expression of 1436 genes in dDG, 987 in vDG, 744 in dCA3, 662 genes in vCA3, 204 in dSub and 972 in vSub. Our results indicate that preconditioning by perforant pathway electrical stimulation may induce a coordinated increase in GABAergic inhibition in both DG regions but not in CA3. Furthermore, we observed changes in synaptic reorganization, increased cholesterol metabolism, and astrogliosis in the subiculum.