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Leung K1.


Molecular Imaging and Contrast Agent Database (MICAD) [Internet]. Bethesda (MD): National Center for Biotechnology Information (US); 2004-2013.
2006 Mar 17 [updated 2008 Jan 12].

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National Center for Biotechnology Information, NLM, NIH, Bethesda, MD


Dopamine, a neurotransmitter, plays an important role in the mediation of movement, cognition, and emotion (2, 3). Dopamine receptors are involved in the pathophysiology of neuropsychiatric diseases such as Parkinson’s disease, Alzheimer's disease, Huntington’s disease, and schizophrenia (4). Five subtypes of dopamine receptors, D1 through D5, have been well characterized pharmacologically and biochemically (5). These five subtypes are classified into two subfamilies: D1-like (D1 and D5) and D2-like (D2, D3, and D4) dopamine receptors. D1-like and D2-like receptors exert synergistic as well as opposite effects at both the biochemical and overall system level. A great majority of striatal D1 and D2 receptors are localized postsynaptically on caudate-putamen neurons and to a lesser extent presynaptically on nigrostriatal axons. (R)-(+)-8-Chloro-2,3,4,5-tetrahydro-3-[11C]methyl-5-phenyl-1H-3-benzazepin-7-ol ([11C]SCH 23390) was the first positron emission tomography (PET) radioligand for D1 receptor studies. However, [11C]SCH 23390 exhibits a low neocortex/cerebellum ratio (1.5), which makes it difficult to estimate the D1 receptor density in the neocortex. (+)-8-Chloro-5-(7-benzofuranyl)-7-hydroxy-3-[11C]methyl-2,3,4,5-tetrahydro-1H-3-benzazepine ([11C]NNC 112) was also found to be a selective, high-affinity antagonist of D1 receptors, but to have only a marginal effect on D2, α1-adrenergic, muscarinic, and histaminergic receptors and only a slight effect on 5-HT2 receptors (6, 7). [11C]NNC 112 was found to display higher specific signal/noise ratios than [11C]SCH 23390. [11C]NNC 112 PET has been developed to study D1 receptor occupancy and density in the striatum and neocortex in humans.

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