Na-G-penicillin penetration into rat cerebral cortex and formation of an epileptic focus.

Fluorescein isothiocyanate-labelled Na-G-penicillin was applied to the intact dura of 11 rats and the cortical layers were determined to which this epileptogenic substance must penetrate for electrophysiologically demonstrable focal activity to be induced. In 10 animals labelled penicillin was demonstrated in cortical layers I--III and in one animal in layers I and II. This concurs with the results obtained in 12 other animals in which activity was recorded from three depths of the cerebral cortex with semimicroelectrodes.