Which statement describes the primary action of benzodiazepines?

Which statement describes the primary action of benzodiazepines?

• A. They block NMDA receptors
• B. They inhibit monoamine oxidase
• C. They antagonize histamine H1 receptors
• D. They modulate GABA to increase Cl- influx

Answer: (D)

Benzodiazepines work by potentiating the inhibitory action of GABA on its receptor. They bind to a specific site on the GABA-A receptor and increase the receptor’s response to GABA, which means the chloride channel opens more readily and for a longer or more frequent duration. This enhances chloride influx into the neuron, hyperpolarizing it and reducing neuronal excitability. They do not directly activate the chloride channel themselves; their effect depends on the presence of GABA. This mechanism explains their sedative, anxiolytic, anticonvulsant, and muscle-relaxant properties. Other options point to actions like NMDA receptor blockade, monoamine oxidase inhibition, or histamine H1 antagonism, which are not how benzodiazepines exert their primary effect.

Benzodiazepines work by potentiating the inhibitory action of GABA on its receptor. They bind to a specific site on the GABA-A receptor and increase the receptor’s response to GABA, which means the chloride channel opens more readily and for a longer or more frequent duration. This enhances chloride influx into the neuron, hyperpolarizing it and reducing neuronal excitability. They do not directly activate the chloride channel themselves; their effect depends on the presence of GABA. This mechanism explains their sedative, anxiolytic, anticonvulsant, and muscle-relaxant properties. Other options point to actions like NMDA receptor blockade, monoamine oxidase inhibition, or histamine H1 antagonism, which are not how benzodiazepines exert their primary effect.