Influence of aminooxyacetic acid on the potassium-evoked release of [3H]gamma-aminobutyric acid from slices of rat cerebral cortex

The release of [3H]GABA from superfused slices of rat cerebral cortex 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 absence of AOAA, omission of Ca2+ from the superfusion medium reduced the release of [3H]GABA evoked by a 30 mM K+ pulse by 81.6%, whereas in comparable experiments carried out in the presence of AOAA omission of Ca2+ reduced the K+-evoked release by only 23.5%. Similar results were obtained when a 50 mM K+ pulse was used, whereupon omission of Ca2+ reduced [3H]GABA release by 78.7% in the absence of AOAA as compared with a reduction of only 47.9% when AOAA was present. It is concluded that the presence of AOAA decreases the Ca2+-dependence of K+-evoked [3H]GABA release in this system