Measurement of release of endogenous GABA and catabolites of [3H]GABA from synaptosomal preparations using ion-exchange chromatography |
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Authors: | Jeffrey Grove Colin R. Gardner Mary H. Richards |
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Affiliation: | (1) Centre de Recherche Merrell International, 16, rue d'Ankara, 67084 Strasbourg Cedex, France |
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Abstract: | Picomole quantities of endogenous GABA in acidified superfusates of synaptosomal preparations have been measured using micro-bore ion-exchange chromatography and post-column formation of the fluorescent iso-indole derivative. Using this technique superfusates have been analyzed directly, without further manipulations, to investigate the release of endogenous GABA. Spontaneous release of GABA was 2–5 pmol/200 l superfusate increasing to 20 pmol/200 l with potassium stimulation. When -vinyl GABA (RMI 71754), an inhibitor of GABA-T was injected into rats (750 mg/kg) and synaptosomes prepared the potassium-evoked release of GABA was increased 3-fold compared to controls. Chromatographic separations and measurement of release of endogenous and radiolabeled GABA allowed the real specific activity of released GABA to be calculated. Only when 500 M amino-oxyacetic acid was added during isolation of synaptosomes was the specific activity of released GABA the same as the initial specific activity. |
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