Abstracts

Rationale: We have recently shown that the occurrence of epilepsy (or status epilepticus - SE - and subsequent seizures) induced progressive cellular/molecular and cytoarchitectural brain abnormalities in both patients affected by focal cortical dysplasia (FCD) and an experimental model of acquired FCD (MAM-pilocarpine- MP- rat; Finardi et al 2013; Colciaghi et al 2011; 2014). We have here exploited MP rats to verify i) the activation of cell death pathways during the course of epilepsy, and ii) the effect of conventional anti-epileptic treatment on seizure recurrence and brain damage. Methods: FluoroJade (FJ) labeling was performed in MP rats at different epilepsy stages, from 18h after SE onset up to 6 months of spontaneous recurrent seizures (SRS) in order to evaluate the localization and extent of degenerating neurons (n=4-6 rats per group). Further, to address i) the relationship between epilepsy per se and brain damage and ii) the feasibility of non-invasive prolonged drug administration, we performed a two-months pilot-trial with carbamazepine (CBZ)-in-food protocol (300 mg/kg/day, Ali et al, 2012) in MP rats treated at seizure onset. Seizure video-monitoring (24h/day), FJ and morphometric analysis were used as readouts of treatment efficacy. Results: FJ staining in MP rats revealed the activation of cell injury not temporally restricted to SE, but extending throughout the different epileptic stages considered. We found a region-specific pattern of FJ activation, degenerating neurons being more evident at early chronic stages (3-5 days of SRS) in neocortex and thalamus and at chronic stages (3-6 months of SRS) in hippocampal CA layers. For the pilot CBZ-trial a total of 9 young-adult MAM rats were pilocarpine treated. Only MP rats experiencing a frank 90 min SE (n=4; Colciaghi et al 2011; 2014) were treated for two months after the onset of the first spontaneous seizure (7-9 days post-SE) with a daily dose of 300 mg/kg CBZ formulated in food pellets. Video-monitoring analysis revealed that CBZ treatment completely blocked spontaneous seizures (stage 1-5 Racine score) in two out of 4 MP/CBZ rats (i.e., MP-CBZ responder rats). Conversely, mild (1 rat) to severe (1 rat) seizure activity (head-nodding/running/jumping/rearing and falling) was observed in the two remaining rats (MP-CBZ non-responders). Morphometric/morphologic analysis demonstrated clear cortical thickness reduction in MP-CBZ non-responder vs responder rats and no FJ+ neurons in MP-CBZ responders, while MP-CBZ non-responder rats exhibited a FJ+ pattern very similar to that observed in 3-months epileptic MP rats. Conclusions: Our data indicate that the MP rat model might represent a proper experimental setting to verify if modulation of seizure expression can prevent brain damage (i.e., no seizures, no brain damage), and demonstrate the direct role of epilepsy in inducing pathologic brain plasticity. Our preliminary data from pilot-CBZ trial support the feasibility of the drug-in-food protocol strategy for prolonged treatments in epilepsy models.