We have recorded the electroretinogram from 19 superfused eyecups of the Xeiiopus retina in order to assess the effects of agonists of the inhibitory neurotransmitter gamma-aminobutyric acid (GA notBA), on both oscillatory potentials and the b-wave. We found that in seven eyecups the GABA uptake blocker nipecotic acid (0.1-5 mM) reduced the amplitudes of the oscillatory potentials, without having an effect on the b-wave unless it was applied in larger doses. The GABAB agonist baclofen (0.05-3 mM) reduced the amplitude of the ERG b-wave selectively in seven eyecups tested, without any effect on the amplitude of the oscillatory potentials. The GABAA agonist aminovaleric acid (0.05-3 mM) on the other hand, selectively reduced the oscillatory potentials in five, but had no reliable effects on the Xenopus b-wave. These results suggest that GABAergic mechanisms related to both A and B receptor types induce different influence on the amplitude of the oscillatory potentials and the b-wave.