Central in Vivo Nicotinic Acetylcholine Receptor Imaging Agents for Positron Emission Tomography (PET) and Single Photon Emission Computed Tomography (SPECT)

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Positron emission tomography (PET) and single photon emission computed tomography (SPECT) are useful for non-invasive investigation of brain receptors. With these imaging techniques, changes in brain receptor densities and distributions during chronic drug treatments and disease progressions can be tracked for a long period. Appropriate radiolabeled imaging agents are necessary for PET and SPECT molecular imaging. Nicotinic acetylcholine receptors (nAChRs) play important roles in brain functions. The α4β2 and α7 are the major nAChR subtypes in the brain. To date, several subtype selective radiolabeled ligands for nAChR have been reported. For the α4β2 subtype, some agents are already applied for human studies, but only a few agents are developed for the α7 subtype. Here, we overview our results of [^125/123I]5-iodo-3-(2(S)-azetidinylmethoxy)pyridine and 5-[¹¹C]methyl-3-(2-(S)-azetidinylmethoxy)pyridine ([¹¹C]5MA) for α4β2 subtype imaging, and [¹¹C](R)-2-methylamino-benzoic acid 1-aza-bicyclo[2.2.2]oct-3-yl ester ([¹¹C](R)-MeQAA) for α7 subtype imaging.