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 (13)C and (15)N 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.