Application Peripheral benzodiazepine ligand useful in distinguishing central-type from peripheral-type benzodiazepine receptors. Biochem/physiol Actions 4′-Chlorodiazepam (Ro5-4864) is a potent selective antagonist of the mitochondrial translocator protein 18kDa (TSPO), formerly known as the peripheral benzodiazepine receptor (PBR). Ro5-4864 does not bind to GABA(A) receptors and lacks typical benzodiazepine effects, but has been found to be neuroprotective in several studies.