That glutamate neurotransmission has become an increasing target of drug development for the treatment of neuropsychiatric and substance use disorders, underscores the significance of developing novel tools to investigate baseline and dynamic fluctuations in glutamate concentrations throughout the human brain. While proton magnetic resonance spectroscopy (1H-MRS) is presently the gold standard for measuring human cortical glutamate concentration, its primary limitations are low spatial resolution and long acquisition times, which preclude imaging of spatial distribution of brain glutamate. Thus, there is clearly an unmet need for a high resolution, nonradioactive imaging tools for cerebral glutamate mapping. The goal of the proposed study is to design, optimize and validate Chemical Exchange Saturation Transfer (CEST) pulse sequences in an animal model in order to facilitate investigation of the glutamate contribution to addiction and neuropsychiatric disorders. Specifically, first, we will develop and optimize CEST imaging pulse sequences via both numerical simulations and experiments on known phantoms and demonstrate the feasibility of detecting glutamate under physiological conditions. Second, these methods will be optimized for in vivo measurements and investigate the potential of detecting glutamate in rat brain modulated by exogenous administration of drugs known to elevate significant glutamate levels within short period of time. The proposed method offers a highly novel, non-invasive, and nonradioactive method of measuring glutamate concentrations in vivo throughout the brain and it has the capacity to outperform 1H-MRS with respect to spatial resolution and sensitivity. In deed, glutamate CEST imaging potentially provides two to three orders of magnitude higher sensitivity than conventional MRS. Once optimized and validated on animal models, these experiments can be readily translated to clinical setting paving the way for human studies dealing with substance abuse as well as other neuropsychiatric disorders.
That glutamate neurotransmission has become an increasing target of drug development for the treatment of neuropsychiatric and substance use disorders, underscores the significance of developing novel tools to investigate baseline and dynamic fluctuations in glutamate concentrations throughout the human brain. Primary limitations of current noninvasive methods for measuring human cortical glutamate concentration are low spatial resolution and long acquisition times. The goal of the proposed study is to design, optimize and validate novel noninvasive, chemical exchange saturation transfer (CEST) based magnetic resonance imaging technology in an animal model in order to facilitate investigation of the glutamate contribution to addiction and neuropsychiatric disorders.
