Effect of phenobarbital on cortical epileptogenic foci in the rat.

The activity of epileptogenic foci was studied in acute experiments on adult male rats without general anaesthesia; the animals first received an intraperitoneal injection of phenobarbital [40 mg/kg] and 30 min later a cortical focus was induced by the local application of penicillin. These foci, which were induced in the sensorimotor area, had a lower discharge frequency than in the controls and the formation of projected discharges was delayed. In two symmetrical and asymmetrical cortical foci, activity was synchronized significantly more slowly after phenobarbital than in the controls. The cortical interhemispheric response was not influenced by the administered dose of phenobarbital. In these experiments, phenobarbital had an anti-epileptic effect both on the primary focus and on the spread of epileptic activity from this focus.