Interaction of 2,3-benzodiazepines with peripheral benzodiazepine receptors

2,3-Benzodiazepines (BZs), such as tofizopam (TP) and GYKI-51 189 have anxiolytic potency accompanied by moderate sedative action, but no anticonvulsant and muscle relaxant activities. These compounds show relatively low affinity to the peripheral benzodiazepine (PBZ) receptors, nevertheless, they decrease the binding of (3H)Ro5-4864 to its receptors in heart, kidney and brain membranes. This diminution in the binding is due to a decrease in the affinity for the ligand (Kd) without any change in the maximal number of binding sites (Bmax). This interaction of 2,3-BZs with PBZ binding sites may explain their pharmacological profile.