sentences:  Early autoradiographic studies using tritiated PK-11195 ([3H]-PK11195) demonstrated that in the central nervous system (CNS) of rodents, 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.