Possible role of dentate gyrus in greneration of rat temporal lobe epilepsy induced by electrical stimulation.

Possible role of the dentate gyrus (DG) and the hippocampus (HPC) in temporal lobe epileptogensis was investigated in an electrogenic model of rat epilepsy. Chronic tetani (60 Hz, 0.4-0.6 mA. 2 s) were administered once daily for 7 days to the right dorsal hippocampus (DHPC) or the right DG. Animal behavior was observed and depth electro-graphic seizures and T(2)-weighted magnetic resonance images (T(2)-WI) were measured. Results indicated that the frequency of primary wet dog shakes (WEDS) in the DG-stimulated rats was much lower than that in the DHPC-stimulated rats (P<0.05). The mean maximal wave-amplitude in DG electrographs was also much lower than that in HPC electrographs (P<0.05). The oscillations proportion of DHPC electrographs increased after DHPC-tetanization (from 2/9 up to 7/9 rats). T(2)-WI hyperintensity in the lateral ventricle area was detected only in the DHPC-tetanized rats, not in the DG-tetanized rats (P<0.05). These results suggest that the DG acts as a filtering site in the entorhinal cortex-HPC neuronal circuitry and its dysfunction causes damage to the HPC and the generation of temporal lobe epilepsy.