Simultaneous determination of γ-aminobutyric acid and glutamic acid in the brain of 3-mercaptopropionic acid-treated rats using liquid chromatography atmospheric pressure chemical ionization mass spectrometry

The measurement of gamma-aminobutyric acid (GABA) and glutamic acid (Glu) in the whole brain and in various regions of the brain in 3-mercaptopropionic acid (3-MPA)-treated rats has been developed using liquid chromatography-mass spectrometry with an atmospheric pressure ionization interface system. The recoveries of these compounds were 94.90+/-4.18% for GABA, 95.60+/-2.86% for Glu after ion-exchange treatment. The detection limits for GABA and Glu were 2.5+/-0.3 mu g/ml and 5.0+/-0.8 mu g/ml, respectively, when 20 mu l sample were injected. GABA concentration in the whole brain decreased gradually to 5 min and reached 63% of normal value after administration of 3-MPA, and the concentration increased gradually thereafter until 60 min. Conversely, the concentration of Glu in the whole brain increased gradually to 10 min and reached 154% of normal value, and after that decreased gradually and reached almost normal level at 60 min after administration of 3-MPA. GABA concentration in various regions of brain decreased to 5 min in all regions after administration of 3-MPA, and reached normal levels at 60 min as in the whole brain. This method was found to be useful for studies of metabolism of GABA and Glu in biological samples. (C) 1999 Elsevier Science B.V. All rights reserved.