Electrocorticographic and behavioral features of turtle parenteral penicillin epilepsy.

The epileptogenic action of parenteral penicillin was studied in turtles with electrodes chronically implanted in both cerebral hemispheres. Penicillin was administered intraperitoneally at doses of 200,000 to 1,600,000 IU/kg. Doses higher than 600,000 IU/kg caused the appearance on the electrocorticogram of bilateral sharp waves or biphasic spikes, sometimes more pronounced in one hemisphere. These events were often accompanied by clonic activity of the neck muscles and mouth movements in an epileptic automatism. Intravenous penicillin (200,000 to 1,000,000 IU/kg) also evoked changes of the basic pattern of the electrocorticogram. Doses up to 350,000 IU/kg induced bilateral sharp waves and/or spikes sometimes accompanied by the seizures described in item 2. Doses above 400,000 IU/kg produced bilateral synchronous spike or polyspike discharges with a clonic-tonic seizure pattern. The same dose of penicillin induced more marked changes in the electrocorticogram when injected intravenously than intraperitoneally. Since larger doses of parenteral penicillin were required to evoke epileptic activity in turtles than in cats, the present results are consistent with the concept that the brain of phylogenetically lower animals is less susceptible to epileptogenic agents than the brain of higher animals.