In Situ 3D MR Metabolic Imaging of Microwave-Irradiated Rodent Brain: A New Tool for Metabolomics Research

The rapid elevation in rat brain temperature achieveable with focused beam microwave irradiation (FBMI) leads to a permanent inactivation of enzymes, thereby minimizing enzyme-dependent post mortem metabolic changes. An additional characteristic of FBMI is that the NMR properties of the tissue are close to those of the in vivo condition and remain so for at least 12 hours. These features create an opportunity to develop MRI and MRS on microwave-irradiated samples into a technique with a resolution, coverage and sensitivity superior to any experiment performed directly in vivo . Furthermore, when combined with pre-FBMI infusion of 13 C-labeled substrates, like [1- 13 C]-glucose, the technique can generate maps of metabolic fluxes, like the TCA and glutamate-glutamine neurotransmitter cycle fluxes at an unprecedented spatial resolution.