Induction of semichronic epileptic foci using cobalt oxide

This paper describes a new method for production of semichronic epileptic foci in the cerebral cortex of cats. Cortical lesions that turned into epileptic foci were induced by extradural application of cobalt oxide powder. These lesions extended through the entire depth of the gray matter, but did not cause gross macroscopic damage. The cobalt oxide powder was removed from the dura mater 7 days after its application, at which time the lesion already showed epileptic activity; this activity did not diminish 7, 14, or 21 days later. Testing of epilepsy was done with a special procedure that allowed work with anesthetized animals. Before treatment with cobalt oxide began, the maximal dose of convulsant drug that would not cause an epileptic electrocorticogram response was determined for each animal (the "trigger dose"). Subsequent testing of potential epileptic foci consisted of monitoring the electrocorticographic responses to rapid intravenous injections of the trigger convulsant dose. The success of the present method in production of epileptic foci is evaluated by several criteria and is compared with other methods.