Magnetic resonance spectroscopic approaches to studying neuronal: glial interactions

In vivo magnetic resonance spectroscopy (MRS) is a noninvasive technique for the measurement of the concentration and synthesis of metabolites in the brain. Application of the state-of-the-art in vivo 13C and 15N MRS techniques to studying the synthesis of glutamate and glutamine has revealed that the glutamate–glutamine cycle between neurons and glia is a major metabolic flux, with a flux rate of 60%–80% relative to neuronal oxidative glucose metabolism in the resting human cerebral cortex. The MRS studies leading to the quantification of the glutamate–glutamine cycling flux are reviewed here. The advantages and limitations of different strategies are also discussed.