Abstracts

Rationale: We recently demonstrated that intrahippocampal microinjection of pilocarpine (PILO) induces behavioral/electrographic status epilepticus (SE) and spontaneous recurrent seizures (SRS) that mimick temporal lobe epilepsy (TLE). In this study we aimed to detect the presence of SE, SRS and Fluoro-Jade (FJ)-positive neurodegeneration induced by intrahippocampal microinjection of star fruit, brute extract or its pure toxin, caramboxin, in comparison with the model of intrahippocampal microinjection of PILO.Methods: Adult male Wistar rats (250-300 g, n=70), were stereotaxically implanted with electrodes/cannulas in the following coordinates aimed to the hippocampal formation: -6,30 mm AP (bregma); -4,5 mm LL (sagittal sutura) and -4,5 mm DV (duramater). All groups were microinjected with 1 μl vehicle (PBS; n=9 controls); 1 μl brute extract of star fruit (n=11) or caramboxin (n=4); 1 μl of vehicle (saline 0.9%; n=18) and 1 μl of PILO (2.4 mg/μl; n=28). Video-EEG (n=24; controls and star fruit) or only video (n=46; controls and PILO) recordings were executed in order to verify the presence of behavioral/EEGraphic SE. The latter was defined as enduring seizures, which in our case were interrupted after 90 minutes of their onset, with diazepam (5 mg/kg; i.p). Animals treated with vehicle and star fruit toxin were video-taped 8 hours a day, during 30 days, to detect behavioral/EEGraphic SRS. Immediately after this period all animals were sacrificed in deep anesthesia. Animals of the PILO group were sacrificed: 12 (n=09), 24 (n=07) and 168 (n=12) hours after SE. In all groups the brain tissue was processed for histochemical determination of the electrode/cannula correct placement (Nissl) and to detect neurodegeneration (FJ). All experimental procedures were approved by the Ethical Committee of our Medical School.Results: Our data demonstrated that intrahippocampal PILO induced SE in 78% of the animals, confirming previous findings from our laboratory. Furthermore, and for the first time, we found in this model FJ-positive neurodegeneration in selective hippocampal subregions. Additionally, after the microinjection of brute extract of star fruit or caramboxin, we observed EEGraphic SE in 100% (n=15) of the animals. Behavioral/EEGraphic SE was detected in only 44% (n=4) of the animals injected with brute extract of star fruit and 50% (n=2) with caramboxin. EEGraphic SRS occurred in 100% of the animals (n=13) and behavioral SRS in 44% of them (n=5). After star fruit (extract or caramboxin) microinjections we detected FJ-positive neurodegeneration in CA1, CA3 and hilus of the dentate gyrus and subiculum. Conclusions: We conclude that the behavioral, EEG and histological events found in both star fruit and PILO models were similar. For those reasons, we propose the protocol of SE, SRS and FJ-positive neurodegeneration induced by intrahippocampal microinjection of star fruit toxin as a new model of TLE. Financial support: FAPESP, CAPES-PROEX, CNPq and FAEPA