Epileptogenic cortical foci were produced by the topical application of cobalt powder to the exposed anterior or posterior sigmoid gyrus of adult cats. Within 60–90 min after application, epileptic discharges were observed only in the area adjacent to the cobalt-treated region (focus). Twenty-four hours later, tonic and clonic epileptic convulsions occurred. These seizures disappeared by the 3rd day after treatment. The concentration of amino acids in the cortex was determined during three periods after the application of cobalt: preconvulsive period (acute), 0–360 min; convulsive period (semi-acute), 24–48 h; postconvulsive period (chronic), 30–70 days.In the cortical tissue adjacent to the site of cobalt application, glutamic acid, aspartic acid, and γ-aminobutyric acid were decreased, while there was a marked increase in glycine, threonine, serine, and taurine during the convulsive period. In the preconvulsive period, the amino acids in the superfusates of the cobalt-treated cortex were measured. The rate of release of glutamic acid increased within 90 min after cobalt application together with a corresponding decrease of the rate of release of glutamine and urea. The excitatory effect of the liberated glutamic acid may play an important role in the production of focal epileptic discharges following the application of cobalt powder to the cerebral cortex.
