Development of PET and SPECT Radioligands for In Vivo Imaging of NMDA Receptors

N-Methyl-d-aspartate receptors (NMDARs) play an important role in the neurotransmission of the central nervous system (CNS). On the other hand, aberrant functioning of the NMDARs has been implicated in various CNS disorders. Positron emission tomography (PET) and single photon emission computed tomography (SPECT) imaging of NMDARs may provide novel insights on CNS functions and various CNS disorders that could lead to the discovery of potential drug therapies. Despite numerous efforts to develop a number of radioligands for NMDARs since the late 1980s, there are no clinically useful in vivo imaging probes. However, recent continuous efforts have provided several promising radiotracers for NMDARs, such as 3-benzazepine derivatives targeting GluN2B. In this chapter, we summarize the progress in the development of PET and SPECT imaging agents for NMDARs and discuss the prospects in this field.