The action of inhibitory neurotransmitters, gamma-aminobutyric acid and glycine may distinguish between the area centralis and the peripheral retina in cats.

The effects of iontophoretically applied gamma-aminobutyric acid (GABA) and glycine, and of their antagonists, bicuculline and strychnine, were compared between ganglion cells from the central and peripheral retinae of optically intact eyes in barbiturate-anaesthetised cats. The visual response of on-cells was inhibited by GABA and enhanced by bicuculline. The visual response of off-cells was inhibited by glycine and enhanced by strychnine. The sensitivity of cells to the transmitters was lower in the peripheral retina than in the area centralis, whilst the sensitivity to the antagonists was similar in both regions of the retina. Cells from the area centralis were inhibited by either GABA or glycine, but never both. Cells from the periphery were less selective and were inhibited by both transmitters.