This proposal outlines new methodologies for synthesizing and testing paramagnetic ligands for the visualization and quantification of neuropeptide receptors in the brain with MRI. The long-term goal of this research is to provide neuroscientists and clinicians with tools for studying the etiology and pathophysiology of mental illness. Ligands for the visualization and quantification of neurotransmitter receptors with MRI would be critical tools in the diagnosis and prognosis of mental illness and the evaluation of psychosocial and therapeutic intervention strategies. Neurotensin, a neuropeptide implicated in the control of schizophrenia is the prototype molecule under development. If successful, these methods will be applied to numerous G protein-coupled receptors whose endogenous ligands are involved in brain function. A non-invasive procedure for imaging receptors with MRI would provide greater spatial and temporal resolution than PET or SPECT and would not require the use of radioactivity. PROPOSED COMMERCIAL APPLICATIONS: Paramagnetic ligands used for the visualization and quantification of neurotransmitter receptors in the brain with MRI have great commercial potential in the area of diagnosis, prognosis and treatment assessment for mental and neurological disorders. Research scientists and clinicians in drug companies, universities, and hospitals would use these tools.