GABA and glycine effects on the bipolar cells of the carp retina

Effects of GABA and glycine applied electrophoretically were examined on bipolar cells in the carp retina. When applied at the outer plexiform layer, GABA produced a small depolarization in on-center cells, but a small hyperpolarization in off-center cells. These effects were concluded to be mediated by photoreceptor cells. When applied at the inner plexiform layer, GABA produced a hyperpolarization in on-center cells but no response in off-center cells. This response was resistant to Co2+ ions. Thus GABA is very like the inhibitory neurotransmitter from amacrine to on-center bipolar cells. Glycine, when applied in either layer, did not have a noticeable effect on either type of bipolar cells.