Fig. 2.
In vivo imaging of microglia in living subjects by microscopic techniques and positron emission tomography (PET). a PET imaging of microglial cells in vivo involves utilizing ligands labeled with radioisotopes such as [11C](R)-PK11195 that bind translocator protein-18 kDa (TSPO, also called the peripheral benzodiazepine receptor (PBR)) expressed on the outer mitochondrial membrane in microglia. The radioisotope undergoes positron emission decay resulting in the emission of a positron, which annihilates with an electron producing a pair of gamma particles that are emitted 180° apart and are detected by the PET scanner. b Microglia are labeled with green florescent protein under control of genetic loci specific to microglia such as CXC3R1 and Iba-1. In such transgenic mice, the skulls of the animals are thinned and animals are imaged with two/multiphoton microscopy. Deep visual penetration and optical sectioning of the tissue enable time-lapse, real-time, 3D imaging of microglia in vivo in live animals