Transition from status epilepticus to interictal spiking in a rodent model of mesial temporal epilepsy

Status epilepticus (SE) is a serious, life-threatening condition requiring immediate care to prevent neuronal injury and long-term functional deficits. SE is modeled in rodents by systemic injection of chemoconvulsants such as pilocarpine, which induces EEG and behavioral activities similar to what seen in humans. Combined injection of diazepam and ketamine is commonly used to terminate SE in rodents but, to date, no study has analysed the EEG activity and behavior during SE and after diazepam + ketamine administration. We therefore performed EEG recordings from the hippocampal CA3 region of mice before and during pilocarpine-induced SE as well as for 24 h after injection of diazepam + ketamine. We found that although convulsive behavior disappeared within 5.5 min ( ± 1.12 min; n = 5) after diazepam + ketamine treatment, EEG epileptiform activity resembling what seen during SE persisted up to 278.8 min ( ± 262.0 min). The end of this SE-like EEG pattern was characterised by transition to high amplitude, persisting interictal spikes. Our findings show that (i) administration of diazepam and ketamine stops behavioral but not EEG epileptiform activity associated to pilocarpine-induced SE; and (ii) such SE-like EEG pattern persists for approx. 4 h to be replaced by interictal spikes that predominate during the so called latent period in this model of mesial temporal lobe epilepsy.