γ-Aminobutyric Acid Stimulates the Release of Endogenous Ascorbic Acid from Rat Striatal Tissue

Abstract: γ-Aminobutyric acid (GABA) was found to induce the release of ascorbic acid from rat striatal homogenates and minces. This release was studied with the use of a rapid supervision system with an on-line amperometric detector that monitors for the presence of easily oxidized substances (i.e., ascorbate, 3,4-dihydroxyphenylethylamine). The release was found to be calcium-independent and depolarization-dependent. This releasable pool of ascorbate could be replenished through nonstereospecific uptake. The releasing action of GABA was mimicked by the GABA agonist, muscimol, and was completely inhibited by the GABA antagonist, picrotoxin. The structural analogues of GABA, β-alanine and γ-hydroxybutyric acid, had no effect. These data indicate that ascorbate release is GABA-receptor mediated and syn-aptically localized.