The peripheral benzodiazepine receptor (PBR) is named for its affinity for benzodiazepines and its initial description in peripheral tissues. This is opposite to the central benzodiazepine receptors (CBRs) of the CNS that are primarily responsible for the relaxant, anticonvulsant, and anxiolytic effects of benzodiazepines. PBR is a transmembrane protein associated with the outer mitochondrial membrane. It has been implicated in several physiological functions, including steroidogenesis, mitochondrial respiratory control, and cell growth, survival, differentiation, and chemotaxis.