Determination of l -glutamic acid and γ–aminobutyric acid in mouse brain tissue utilizing GC–MS/MS

A rapid and selective method for the quantitation of neurotransmitters, l-Glutamic acid (GA) and γ–Aminobutyric acid (GABA), was developed and validated using gas chromatography-tandem mass spectrometry (GC–MS/MS). The novel method utilized a rapid online hot GC inlet gas phase sample derivatization and fast GC low thermal mass technology. The method calibration was linear from 0.5 to 100 μg/mL, with limits of detections of 100 ng/mL and 250 ng/mL for GA and GABA, respectively. The method was used to investigate the effects of deletion of organic anion transporter 1 (Oat1) or Oat3 on murine CNS levels of GA and GABA at 3 and 18 mo of age, as compared to age matched wild-type (WT) animals. Whole brain concentrations of GA were comparable between WT, Oat1(−/−), and Oat3(−/−) 18 mo at both 3 and 18 mo of age. Similarly, whole brain concentrations of GABA were not significantly altered in either knockout mouse strain at 3 or 18 mo of age, as compared to WT. These results indicate that the developed GC–MS/MS method provides sufficient sensitivity and selectivity for the quantitation of these neurotransmitters in mouse brain tissue. Furthermore, these results suggest that loss of Oat1 or Oat3 function in isolation does not result in significant alterations in brain tissue levels of GA or GABA.