Which neurotransmitter system is most directly linked to inhibitory control in the CNS, commonly targeted by sedatives including benzodiazepines?

• A. Dopamine
• B. GABA
• C. Glutamate
• D. Serotonin

Answer: (B)

The main concept here is how inhibitory control in the CNS is governed by GABA and how sedatives like benzodiazepines exploit that system. GABA is the brain’s primary inhibitory neurotransmitter; when it binds to its receptors, it opens chloride channels and hyperpolarizes neurons, reducing their excitability and dampening overall neural activity. Benzodiazepines don’t activate the receptor directly. Instead, they bind to a specific allosteric site on the GABA-A receptor and increase GABA’s effect—making it more likely the chloride channel opens in response to GABA. This amplification of inhibitory signaling produces the familiar sedative, anxiolytic, and anticonvulsant effects. In contrast, dopamine is more tied to reward and motor pathways, glutamate is the main excitatory neurotransmitter, and serotonin modulates mood and sleep but does not mediate the direct inhibitory control that benzodiazepines enhance.