Midazolam exerts its sedative effects by binding at which site on the GABA-A receptor?

• A. The benzodiazepine binding site
• B. The NMDA receptor site
• C. The GABA binding site
• D. The chloride channel pore

Answer: (A)

Midazolam binds to the benzodiazepine site on the GABA-A receptor, an allosteric site separate from where GABA itself binds. As a positive allosteric modulator, it does not activate the receptor by itself but enhances GABA’s effect, increasing the frequency of chloride channel openings when GABA binds. This boosts chloride influx, causing neuronal hyperpolarization and reduced excitability, which produces sedation, anxiolysis, and other benzodiazepine effects. The binding site is distinct from the GABA binding site, the NMDA receptor site, and the chloride channel pore, and the drug’s action depends on the presence of GABA.