Localisation of sites of GABA catabolism in the rat retina

Abstract

GAMMA aminobutyric acid (GABA) has been demonstrated in invertebrate and vertebrate retinae^1,2,3 and has been shown to have an inhibitory action on retinal neurones⁴. In vivo studies of ³H-GABA uptake by rabbit retina have shown a distribution of radioactivity in the inner plexiform layer, the amacrine cells of the inner nuclear layer, the ganglion cell and nerve fibre layers⁵. Further studies have shown that all layers of the rat retina except the outer zone of the rods will accumulate ³H-GABA in vitro⁶ in the presence of amino-oxyacetic acid (AOAA), an inhibitor of GABA metabolism⁷. Uptake was most pronounced in the ganglion cell and nerve fibre layer, inner nuclear and outer plexiform layers and at the outer limiting membrane. Furthermore, it was suggested that ³H-GABA might be largely taken up by Müller's fibres and their nuclei rather than by amacrine cells in the inner nuclear layer of the retina.