How do benzodiazepines act on GABA receptors?

Benzodiazepines primarily act as allosteric modulators at GABA-A receptors, which is why this answer is accurate. GABA-A receptors are ionotropic receptors that, when activated by the neurotransmitter GABA, allow chloride ions to flow into the neuron, leading to hyperpolarization and decreased neuronal excitability. Benzodiazepines bind to a specific site on the GABA-A receptor, distinct from the GABA binding site, enhancing the receptor's affinity for GABA. This allosteric modulation increases the frequency of chloride channel opening when GABA is present, thereby potentiating its inhibitory effects on neurotransmission.

This mechanism is central to the anxiolytic, sedative, and muscle relaxant properties of benzodiazepines. The other options do not accurately describe the action of benzodiazepines: they do not activate GABA-B receptors, inhibit serotonin reuptake, or exhibit antagonistic activity at glutamate receptors. Each of these processes involves different neurotransmitter systems or types of receptors that do not relate to the primary pharmacological effects of benzodiazepines.