Seizures in the intrahippocampal kainic acid epilepsy model: Characterization using long-term video-EEG monitoring in the rat

Objective - Intrahippocampal injection of kainic acid (KA) in rats evokes a status epilepticus (SE) and leads to spontaneous seizures. However to date, precise electroencephalographic (EEG) and clinical characterization of spontaneous seizures in this epilepsy model using long-term video-EEG monitoring has not been performed.
Materials and Methods - Rats were implanted with bipolar hippocampal depth electrodes and a cannula for the injection of KA (0.4 μg/0.2 μl) in the right hippocampus. Video-EEG monitoring was used to determine habitual parameters of spontaneous seizures such as seizure frequency, severity, progression and day-night rhythms.
Results - Spontaneous seizures were detected in all rats with 13 out of 15 animals displaying seizures during the first eight weeks after SE. A considerable fraction (35%) of the spontaneous seizures did not generalize secondarily. Seizure frequency was quite variable and the majority of the KA-treated animals had less than one seizure per day. A circadian rhythm was observed in all rats that showed sufficient seizures per day.
Conclusions - This study shows that the characteristics of spontaneous seizures in the intrahippocampal KA model display many similarities to other SE models and human temporal lobe epilepsy.