The effect of GABAergic blockade by picrotoxin on ganglion cells (GC) activity was investigated in perfused dark adapted eyecups of frog ( Rana ridibunda). PT had diverse effects on the light responses of GC in contrast to its uniform potentiating effect on the amplitude of the ERG b- and d-wave. In some ( n=32) of PT-sensitive ON–OFF GC the ON and OFF responses were changed in a similar manner (both responses were potentiated or both were inhibited), but in the other ( n=10) the both responses were changed in a different manner. PT influenced differentially the activity of OFF GC ( n=17) as well. It not only potentiated or inhibited their light responses, but changed also the temporal characteristics of the responses. Some tonic cells became phasic ones and in some phasic cells a late component appeared under the influence of PT. In some cases ( n=4) the GABAergic blockade changed the apparent cell's type, because of appearance of a new type of response (ON or OFF) non-existing before the blockade. Our results indicate that the GABAergic interneurons are involved in different networks in the inner plexiform layer of frog retina.