Structural changes in cerebral cortex during cobalt-induced epilepsy in the rat

Rods of cobalt metal were inserted into rat cerebral cortex to produce experimental epilepsy. Brain sections were then stained and examined for structural changes at several survival times. Times were based on previous electrocorticographic studies. Comparisons were made with tissue from rats implanted with non-epileptogenic copper or glass rods. Gliosis was much more extensive after copper than after cobalt. Silver-staining revealed unusual , dark granules associated with neurons only in the cobalt-treated rats. Three weeks after cobalt treatment, enlarged perikarya were observed around the implant. The possible significance of these findings is discussed.