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

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 alpha 4 beta 2 find alpha 7 are the major nAChR subtypes in the brain. To date, several subtype selective radiolabeled ligands for nAChR have been reported. For the alpha 4 beta 2 subtype, some agents are already applied for human studies, but only a few agents are developed for the alpha 7 subtype. Here, we overview our results of [I-125/123]5-iodo-3-(2(S)-azetidinylmethoxy)pyridine and 5-[C-11]methyl-3-(2-(S)-azetidinylmethoxy)pyridine ([C-11]5MA) for alpha 4 beta 2 subtype imaging, and [C-11](R)-2-methylamino-benzoic acid 1-aza-bicyclo[2.2.2]oct-3-yl ester ([C-11](R)-McQAA) for alpha 7 subtype imaging.