PK-11195

PK-11195 is an isoquinoline carboxamide which binds selectively to the peripheral benzodiazepine receptor (PBR) (also known as the mitochondrial 18 kDa translocator protein or TSPO). It is one of the most commonly used PBR ligands due to its high affinity for the PBR in all species, although it is starting to be replaced by newer and more selective ligands.

Early autoradiographic studies using tritiated PK-11195 ([3H]-PK11195) demonstrated that in the central nervous system (CNS) of rodent, it binds primarily to the ependymal walls, choroid plexus, and olfactory bulb. However, in the injured nervous system there is a robust and widespread increase in [3H]-PK11195 binding. The binding sites have since been determined to be on glial cells, including microglia, astrocytes, and infiltrating macrophages. The binding of [3H]-PK11195 is considered to be a useful tool in the assessment of neuronal damage.

In addition to being a marker of neuronal damage in animal models of CNS damage, PK-11195 has been used successfully with human brain imaging techniques. [11C](R)-PK11195 has been used in positron emission tomography (PET) scanning to visualize brain inflammation in patients with neuronal damage. Increases in [11C](R)-PK11195 binding have been reported in patients with stroke, traumatic brain injury and in patients with chronic neurodegenerative conditions including Huntington's disease and Parkinson's disease.