GABA-antagonists and spatial summation in Y-type cat retinal ganglion cells.

1. The effect of GABA-antagonists on centre size of Y-type retinal ganglion cells was measured under conditions which ensured that cells were rod driven. 2. Both bicuculline and picrotoxin, administered intravenously, led to reliable and reversible changes in centre size as determined by area-sensitivity measurements. 3. The administration of GABA-antagonists produced opposite results in on- and off-centre cells; the centre summing area decreased in on-centre cells and increased in off-centre cells.