mG2N001 is a negative allosteric modulator (NAM) ( IC 50 : 93 nM) of the metabotropic glutamate receptor mGluR2 and binds to mGluR2 as an antagonist (Ki: 63 nM). mG2N001 is microparticle- and plasma-stable, and its radioisotope [11C] mG2N001 can be used in PET imaging. [11C] mG2N001 has good brain heterogeneity and brain penetration, and can selectively accumulate in mGluR2-rich regions, producing high-contrast brain images.