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

In this study [2‐ 13 C] γ‐aminobutyric acid (GABA) was spectrally resolved in vivo and detected simultaneously with [4‐ 13 C]glutamate (Glu) and [4‐ 13 C]glutamine (Gln) in the proton spectra obtained from a localized 40 μL voxel in rat neocortex with the use of an adiabatic 1 H‐observed, 13 C‐edited (POCE) spectroscopy method and an 89‐mm‐bore vertical 11.7 Tesla microimager. The time‐resolved kinetics of 13 C label incorporation from intravenously infused [1‐ 13 C]glucose into [4‐ 13 C]Glu, [4‐ 13 C]Gln, and [2‐ 13 C]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‐ 13 C]GABA from [1‐ 13 C]glucose in intact rat brain, the rate of 13 C incorporation from [1‐ 13 C]glucose into [2‐ 13 C]GABA in the gabaculine‐treated rats was found to be significantly reduced as a result of the blockade of the GABA shunt. Magn Reson Med 53:1258–1267, 2005. Published 2005 Wiley‐Liss, Inc.