Center for Magnetic Resonance and Optical Imaging, Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
Nat Med. 2012 Jan 22;18(2):302-6. doi: 10.1038/nm.2615.
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.
谷氨酸是大脑中的一种主要神经递质，其胺基与体相水之间存在 pH 值和浓度依赖性的化学交换饱和转移效应（GluCEST），具有通过磁共振进行体内成像的潜力。谷氨酸 CEST 的不对称性在体相水的约 3 ppm 场强下被观察到。在大鼠大脑的大脑中动脉闭塞中，与对侧相比，同侧的 GluCEST 升高了约 100%，主要归因于 pH 值的变化。在血脑屏障破坏的大鼠脑肿瘤模型中，静脉内谷氨酸注射导致 GluCEST 明显升高，谷氨酸的质子磁共振波谱信号也有类似的增加。还获得了来自健康人脑的 GluCEST 图谱。这些结果表明，使用 GluCEST 来映射体内谷氨酸浓度以及 pH 值的相对变化是可行的。还讨论了其他脑代谢物对 GluCEST 效应的贡献。
