Ictal-direct current (DC) shifts precede high frequency oscillations (HFOs) and conventional ictal EEG patterns in human epilepsy patients. However, the role of DC shifts in ictal EEG activities and HFOs is still unknown. Here, we analyzed the wide-band EEG recorded from the PILO-induced acute SE model (400 mg/kg, i.p.) and the PILO-induced chronic TLE model (after 11-13 weeks from 450 mg/kg, i.p.). Our results showed that all seizures during PILO-induced SE yielded DC shifts, which appeared immediately after the onset of ictal EEG patterns and HFOs. Meanwhile, PILO-induced chronic TLE showed two types of ictal EEG patterns, i.e., the one starts with DC shifts followed by conventional ictal EEG patterns and HFOs whereas the another starts with the conventional ictal patterns without DC shifts. These findings highlight the difference in the ictal-DC shifts mechanisms between acute and chronic epilepsy stages, the ictal-DC shifts in acute SE are probably due to massive elevation of extracellular K+ originated from neural firing whereas those in chronic TLE possibly due to the dysfunction of astrocytic K+ buffering.

To: 要旨(抄録)