GABAergic synapses do not contribute to PSS. (A) Raster plots for the spike activity recorded from an MLI during 1 s optical activation under control conditions (upper panel) and after the addition of 30 μM of the GABA-A R antagonist SR95531 to the bathing solution (lower panel, starting 4 min after the drug was added to the bath). (B) Raster plots from a different MLI subject to 1 s optical activation under control conditions (upper panel) and after the addition of 40 μM of the GABA-B R antagonist CGP 55845 to the bathing solution (lower panel, starting 7 min after the drug was added). (C) Pooled data on the ratio of the spike rate during the 1 s period after the end of the light pulse over the spike rate preceding the light.