The term benzodiazepine refers to the portion of the structure composed of a benzene ring (A) fused to a seven membered diazepine ring (B). Benzodiazepine is a central nervous system depressants, a sedative hypnotic agent. Benzodiazepine receptors are located on the alpha subunit of the GABA receptor located almost exclusively on postsynaptic nerve endings in the CNS (especially cerebral cortex). Benzodiazepines enhance the GABA transmitter in the opening of postsynaptic chloride channels which leads to hyperpolarization of cell membranes.