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Rapid assay for gamma-aminobutyric acid in mouse brain synaptosomes using gas chromatography-mass spectrometry
J Palaty1, R Burton, F S Abbott
1Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, Canada.
Abstract:
A sensitive and efficient assay for gamma-aminobutyric acid (GABA) was applied to fresh mouse whole brain synaptosomes where the extracted GABA was analyzed as its di(tert.-butyl(dimethylsilyl)) derivative by gas chromatography-mass spectrometry (GC-MS) using GABA-d6 as an internal standard. Endogenous levels of 20.01 +/- 0.75 nmol GABA/mg protein were found. The method is characterized by a detection limit of about 10 fmol injected GABA derivative and coefficients of intra-day and inter-day variation of 0.95% and 7.7%, respectively. The rate of synaptosomal GABA synthesis was used to determine the activity of glutamate decarboxylase (GAD) as 314.9 +/- 9.0 nmol GABA/mg protein/h. Both GABA levels and GAD activity were significantly elevated by therapeutic doses of the antiepileptic drug valproic acid.