In vivo detection of cortical GABA turnover from intravenously infused [1-13C]D-glucose

Abstract

In this study [2-13C] γ-aminobutyric acid (GABA) was spectrally resolved in vivo and detected simultaneously with [4- 13C]glutamate (Glu) and [4-13C]glutamine (Gln) in the proton spectra obtained from a localized 40 μL voxel in rat neocortex with the use of an adiabatic 1H-observed, 13C-edited (POCE) spectroscopy method and an 89-mm-bore vertical 11.7 Tesla microimager. The time-resolved kinetics of 13C label incorporation from intravenously infused [1-13C]glucose into [4-13C]Glu, [4- 13C]Gln, and [2-13C]GABA were measured after acute administration of gabaculine, a potent and specific inhibitor of GABA-transaminase. In contrast to previous observations of a rapid turnover of [2-13C]GABA from [1-13C]glucose in intact rat brain, the rate of 13C incorporation from [1-13C]glucose into [2-13C]GABA in the gabaculine-treated rats was found to be significantly reduced as a result of the blockade of the GABA shunt.