Abstracts

Rationale: Temporal lobe epilepsy (TLE) is typified by multiple epileptogenic changes in the hippocampus, which contribute to the occurrence of spontaneous recurrent seizures (SRS). In addition, the hippocampus displays reduced concentration of fibroblast growth factor-2 (FGF-2), a growth factor having neural stem cell stimulating, neuroprotective, anticonvulsant, antiepileptogenic and antiinflammatory properties. Reduced FGF-2 concentration is also associated with greatly declined neurogenesis and inflammation in the hippocampus and memory and mood impairments. To understand links between these alterations, we investigated the effects of FGF-2 treatment in the chronic phase of TLE on SRS, cognitive, memory and mood dysfunction using a rat model. Methods: We induced status epilepticus (SE) in young adult F344 rats via graded intraperitoneal injections of kainic acid (5 mg/Kg/hr for 2-4 hrs). After 2 hrs of SE, seizures were terminated through an injection of diazepam (5 mg/Kg) and the frequency of SRS was quantified at 2-4 months after SE. Chronically epileptic rats (CERs) exhibiting comparable frequency of SRS were next randomly assigned to one of the two groups: CER group receiving FGF-2 and epilepsy-only controls. CERs in the FGF-2 group received SQ injections of FGF-2 daily for two weeks at a dose of 40ng/gm/day. The behavioral SRS and cognitive, memory and mood function were quantified in the subsequent months followed by three weeks of continuous electroencephalographic (EEG) recordings. Following this, animals were euthanized and brain tissues were processed for analyses of neurogenesis and inflammation in the hippocampus. Results: Evaluation of SRS revealed that FGF-2 treatment decreased the frequency and intensity of SRS in CERs. In the early post-treatment phase, the reductions were 29% for the frequency of SRS (p>0.05), 66% for Stage-V SRS p < 0.0001), 79% for the duration of individual SRS (p < 0.0001), and 44% for the total time spent in SRS activity (p < 0.001). The decreases persisted in the third month after treatment (27% for SRS, p < 0.05; 67% for Stage-V SRS, p < 0.001; 30% each for the duration of individual SRS and total time spent in SRS, p < 0.05). Moreover, quantification of 7 days of EEG recordings in the 5th month after FGF-2 treatment revealed reduced frequency and intensity of SRS in FGF-2 treated rats, in comparison with the epilepsy-only group. The reductions were 51% each for the frequency of SRS and Stage-V SRS (p < 0.0001) and 55% for the total time spent in SRS (p < 0.001-0.0001). Further, FGF-2 treated CERs displayed ability for novel object recognition, discerning minor changes in object location and pattern separation in novel object recognition, objection location and pattern separation tests, in contrast to epilepsy only controls displaying significant impairments. Additionally, FGF-2 treated rats exhibited a clear affinity for drinking sucrose-containing water in a sucrose preference test whereas epilepsy-only controls showed anhedonia. Analyses through doublecortin immunostaining (which detects the status of neurogenesis in the two weeks prior to euthanasia) did not show increased hippocampal neurogenesis in FGF-2 treated CERs however. Examination through immunostaining for ED-1 (a marker of activated microglia) suggested decreased inflammation in the dentate hilus of FGF-2 treated CERs. Additional analyses of hippocampal neurogenesis at an early time-point after FGF-2 treatment are in progress. Conclusions: The results imply that FGF-2 treatment in the chronic phase of TLE can considerably ease the frequency and intensity of SRS and improve cognitive, memory and mood function. Funding: Supported by Merit Review and Research Career Scientist Awards from the Department of Veteran Affairs to A.K.S.