Absence of electrographic seizures after transient forebrain ischemia in the Mongolian gerbil.

EEG was continuously recorded from Mongolian gerbils for 4 days after transient bilateral forebrain ischemia, to determine whether ischemic brain damage in this species is necessarily associated with seizures. Gerbils were chronically implanted with EEG recording electrodes in hippocampal area CA1, striatum and frontal neocortex and were subjected to a 5-10 min occlusion of both common carotid arteries. During the first few hours after the occlusion, the EEG was dominated by slow waves similar to those recorded from human brain after a damaging episode of cerebral ischemia. Amplitudes of the hippocampal and striatal EEG declined markedly with time, presumably as a result of neuronal degeneration. Ictal activity was never recorded, even from animals that suffered extreme damage to the hippocampal formation and striatum. Therefore ischemic brain damage in the gerbil does not result from seizure activity.