In vivo Detection of Metabolic Turnover of GABA and Glutamate in Human Brain using Dynamically Acquired MEGA-PRESS MRS During 13C-Labeled Glucose Infusion

Glucose, the main substrate for cerebral energy metabolism, serves as a metabolic precursor for both glutamate and GABA synthesis. In the current study, we employ a novel approach to investigate ¹³C-labeling of both glutamate and GABA in the human brain. Specifically, localized homonuclear (¹H) J-difference edited (MEGA-PRESS) MRS spectra were acquired dynamically (without heteronuclear decoupling or editing pulses) to detect glutamate and GABA labelling following an infusion of ¹³C labeled glucose. Despite excellent spectral quality and temporal stability, little or no GABA labeling was observed, raising some questions as to the functional status of the GABA pools detected by MEGA-PRESS.