Since P2Y12 receptors are the only identified target exclusively expressed on M2-type microglia, PET imaging of this receptor could help detect the precise role of microglial phenotype in each stage of neuroinflammation and identify stages of the neurodegeneration diseases. Thus, an antagonist of P2Y12R (sulfonylureas compound 5, with IC50 = 6 nM)300 was radiolabeled with 11C to produce [11C]5, as shown in Figure 9 and used as a PET tracer for evaluation of the P2Y12 receptor301 function in MS disease progression.24,302 Unfortunately, [11C]5 was shown to be an unstable tracer that metabolized rapidly in plasma and in an ex vivo biodistribution study in rats, and only very low brain uptake of this radioligand was detected in this study.302 Therefore, its use for PET imaging of the P2Y12 receptor is not favored.
