Lack of Fos-like immunoreactivity after spontaneous seizures or reinduction of status epilepticus by pilocarpine in rats.

Acute seizures and status epilepticus induced by pilocarpine lead to the expression of Fos-like immunoreactivity in several specific brain areas in a manner similar to that of other models of limbic seizures. Upon development of status epilepticus after systemic pilocarpine injection, animals develop a state where chronic spontaneous seizures recur. Assessment of Fos-like immunoreactivity after such spontaneous seizures or after status epilepticus reinduction reveals either lack of staining or a weak reaction in a few brain areas including the ventral tip of the dentate gyrus, prepiriform, lateral piriform and perirhinal cortices, and scattered locations throughout temporal neocortex. Our results suggest that status epilepticus induction may lead to a long-lasting state of Fos down-regulation.