Figure 10-14 Model of the γ-aminobutyric acid (GABA)-benzodiazepine receptor complex. Current data suggest a pentameric protein composed of α-, β-, and γ-subunits; the proposed arrangement of subunits is arbitrary. There are two sites for GABA binding (on the β-subunits) and a single site for benzodiazepine (BDZ) binding (depicted on the γ₂ -subunit). Homology between the GABA_α receptor and the nicotinic acetylcholine receptor suggests that the chloride ion channel is formed by contributions from each subunit. (Redrawn with modification from Zorumski CF, Isenberg KE: Insights into the structure and function of GABA-benzodiazepine receptors: Ion channels and psychiatry. Am J Psychiatry 148:162, 1991.)