Aspartate Aminotransferase for Synthesis of Transmitter Glutamate in the Medulla Oblongata: Effect of Aminooxyacetic Acid and 2‐Oxoglutarate

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Abstract
The effects of aminooxyacetic acid (AOAA), a transaminase inhibitor, and 2-oxoglutarate, a precursor to glutamate by the activity of aspartate aminotransferase (AAT), on slices of rat medulla oblongata, cerebellum cerebral cortex, and hippocampus were studied. The slices were superfused and electrically stimulated. There was a Ca2+-dependent stimulus-evoked release of endogenous glutamate, .gamma.-aminobutyric acid (GABA), and .beta.-alanine in all regions examined. AOAA (10-4 and 10-3 M) decreased the release of glutamate in the medulla oblongata and cerebellum but not in the hippocampus. L-Canaline, a specific inhibitor of ornithine aminotransferase, did not affect the glutamate release in the medulla. 2-Oxoglutarate (10-3 M) increased the release of glutamate in the medulla oblongata and cerebellum but no in the cerebral cortex and hippocampus. Treatment with AOAA (10-4 M) almost abolished the activities of AAT in all regions studies. AOAA (10-4 and 10-3 M) increased the stimulus-evoked release of GABA in the cerebellum, cerebral cortex, and hippocampus, whereas the stimulus-evoked release of .beta.-alanine was decreased by this agent in all regions studied. These results suggest the participation of AAT in the synthesis of the transmitter glutamate in the medulla oblongata and cerebellum of the rat.