Effect of gamma-vinyl GABA on human pattern evoked visual potentials.

We studied the effects on human visual evoked potentials of gamma-vinyl GABA, an anticonvulsant drug that increases cerebral levels of gamma-aminobutyric acid. The subjects were 15 epileptic patients undergoing a clinical trial of this drug. Serial recordings were made from each patient periodically for 1 year. The stimulus was a reversing checkerboard pattern with a check size of 50 minutes. Plasma levels of other antiepileptic medications remained constant throughout the study. No changes, other than a normal variation of +/- 5 msec, were observed in peak latency throughout the study. These results indicate that there are no GABA-ergic effects on the P100 component evoked by large checkerboard pattern-reversal.