Depressed excitability and integrated EEGs following hippocampal afterdischarges

Rats with chronic hippocampal electrode implants had afterdischarges induced with electrical stimulus intensities of 115, 200, and 800% of a previously determined threshold. Afterdischarge duration, postictal EEG depression duration, and the duration of postictal electrical hypoexcitability were assessed. After discharge duration varied inversely with stimulus intensity as did the duration of postictal hypoexcitability. However, the duration of postictal EEG depression increased with stimulus intensity. This dissociation between postictal neuroexcitability and EEG depression is discussed in terms of possible underlying cholinergic mechanisms.