EEG changes induced by convulsants interfering with GABAergic inhibition in rats. I. Cortical recordings.

Electrocorticographic changes induced by 3 convulsant drugs interfering with the GABA system were studied in 73 adult rats. Aminooxyacetic acid first elicited changes (periods of theta waves) nearly constantly in occipital regions. Bicuculline induced not only occipital theta waves but also groups of spikes with the same frequency in frontal regions; there was no predominance of one of these regions. 3-Mercaptopropionic acid invariably elicited groups of spikes in the frontal region as the first sign of its action. As it progressed, this rhythmic activity became generalized so that differences among the 3 drugs disappeared. Paroxysmal activity induced by the 3 drugs studied was identical. It always started with rhythmic spikes which were gradually transformed into spike-and-wave rhythm. Differences among the 3 convulsants studied were found in the very first electrocorticographic changes. Long latency to the onset of action of 3-mercaptopropionic acid and especially of aminoocyacetic acid qualifies these drugs for studies of preparoxysmal changes.