STRONG INDUCTION OF C-FOS IN THE PIRIFORM CORTEX DURING FOCAL SEIZURES EVOKED FROM DIFFERENT LIMBIC BRAIN SITES

Focal seizures in rats were elicited by electrical stimulation (using parameters necessary for induction of kindling) of the amygdala or two different sites of the piriform cortex, including the previously described 'area tempestas' [26]. Although seizures were behaviorally and electrophysiologically identical, a different pattern of induction of the proto-oncogene c-fos was found. Only the ipsilateral piriform cortex showed strong immunohistochemical labeling of Fos protein, regardless of stimulation site, while the hippocampus was not labeled after focal seizures. It is concluded that the piriform cortex is the epileptogenic focus of limbic seizures, at least during the first stages of electrical kindling.