KAINIC ACID-INDUCED HIPPOCAMPAL SEIZURES IN RATS - COMPARISONS OF ACUTE AND CHRONIC SEIZURES USING INTRAHIPPOCAMPAL VERSUS SYSTEMIC INJECTIONS

Hyppocampal epilepsy is a recently defined syndrome occurring in 65% of all temporal lobe epilepsies as defined by: 1) electrographic (EEG) onset in the hippocampus (HC) prior to EEG seizures elsewhere, 2) post-resection hippocampal sclerosis and messy fiber synaptic reorganizations and 3) relief of typical complex partial seizures after surgical resection of the hyppocampus. We used intrahippocampal kainic acid injections V-2 in vats at different developmental ages (postnatal 7 through adult) to develop long term spontaneous HC EEG spikes, EEG seizures, and behavioral seizures. Split-screen video/EEG EEG monitoring demonstrated that this intrahippocampal kainic acid model produced progressive development of: I) ipsilateral interictal spikes, 2) later polyspike complexes, 3) bilaterally-asynchronous EEG spiking, 4) unilateral HC EEG seizure onsets with occasional secondarily generalized spread to apposite HC and motor cortex to elicit complex partial seizures, and 5) in all seizing rats there was mossy fiber synaptic reorganization, even when injected at age 7 days. These results indicate that the intrahippocampal kainic acid injection model is similar to human hippocampal epilepsy.