Effect of dark adaptation on the GABA system in retina

Abstract

The levels of l-glutamate-1-car☐y-lyase (GAD), 4-aminobutyrate-2-oxoglutarate-aminotransferase (GABA-T) and free amino acids, and the active accumulation of [ 3H]GABA and [ 14C]taurine have been measured in light- and dark-adapted retinae from rat, chicken, frog and goldfish. No significant changes in any of these parameters with state of adaptation to light were evident in rat or chicken retina. However, in retinae from goldfish and frog respectively, decreases in [ 3H]GABA accumulation and GAD activity were noted in the dark. In both cases these changes were accompanied by a fall in the endogenous GABA content of the tissue, but this difference was only significant in goldfish retina.