title: Magnetic resonance imaging of glutamate.
abstract: Glutamate, a major neurotransmitter in the brain, shows a pH- and concentration-dependent chemical exchange saturation transfer effect (GluCEST) between its amine group and bulk water, with potential for in vivo imaging by nuclear magnetic resonance. GluCEST asymmetry is observed ∼3 p.p.m. downfield from bulk water. Middle cerebral artery occlusion in the rat brain resulted in an ∼100% elevation of GluCEST in the ipsilateral side compared with the contralateral side, predominantly owing to pH changes. In a rat brain tumor model with blood-brain barrier disruption, intravenous glutamate injection resulted in a clear elevation of GluCEST and a similar increase in the proton magnetic resonance spectroscopy signal of glutamate. GluCEST maps from healthy human brain were also obtained. These results demonstrate the feasibility of using GluCEST for mapping relative changes in glutamate concentration, as well as pH, in vivo. Contributions from other brain metabolites to the GluCEST effect are also discussed.
authors.affiliation: Center for Magnetic Resonance and Optical Imaging, Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: Kejia
authors.initials: K
authors.lastname: Cai
authors.forename: Mohammad
authors.initials: M
authors.lastname: Haris
authors.forename: Anup
authors.initials: A
authors.lastname: Singh
authors.forename: Feliks
authors.initials: F
authors.lastname: Kogan
authors.forename: Joel H
authors.initials: JH
authors.lastname: Greenberg
authors.forename: Hari
authors.initials: H
authors.lastname: Hariharan
authors.forename: John A
authors.initials: JA
authors.lastname: Detre
authors.forename: Ravinder
authors.initials: R
authors.lastname: Reddy
mesh_terms: D000328:Adult; D000818:Animals; D001921:Brain / Q000378:metabolism*; D001932:Brain Neoplasms / Q000378:metabolism; D018698:Glutamic Acid / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D059906:Neuroimaging / Q000379:methods; D051381:Rats
chemical_list: D018698:Glutamic Acid