Effect of aminooxyacetic acid on γ-aminobutyric acid release from frog retina

The Ca 2+-dependence of the release of [ 3H]γ-aminobutyric acid (GABA) from the pre-loaded, superfused frog retina was investigated in the presence and absence of the GABA-transaminase inhibitor, aminooxyacetic acid (AOAA). In the latter case, an ion-exchange column Chromatographic technique was used to separate [ 3H]GABA from tritiated metabolites released with it into the superfusate. In the presence of aminooxyacetic acid, a 2 min 30 mM K + pulse released similar amounts of [ 3H]GABA in normal and Ca 2+-free Ringer solutions. However, when aminooxyacetic acid was absent, the K +-evoked release of [ 3h]gaba was substantially reduced under Ca 2+-free conditions. It is concluded that the presence of aminooxyacetic acid can reduce the Ca 2+-dependence of K +-evoked release of GABA from the frog retina. This is in accordance with its effect on cerebral cortex of the rat, reported previously.