Benzodiazepines bind two types of receptors, the central γ-aminobutyric acid A receptor and the peripheral translocator protein (TSPO). PK 11195 binds the peripheral benzodiazepine receptor, TSPO, with selectivity and high affinity (Ki = 3.1 nM in cerebellum, 4.1 nM in spinal cord). PK 11195, which lacks the 7-member heterocycle of diazepines, blocks binding of typical benzodiazepines to TSPO. In addition, the binding of labeled PK 11195 to tissues is used to detect the presence of TSPO by various methods. PK 11195 has been used to study the ligand binding site of the B. cereus TSPO.
