Which neurotransmitter is associated with inhibitory signaling in the brain?

Which neurotransmitter is associated with inhibitory signaling in the brain?

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

Answer: (A)

Inhibitory signaling in the brain centers on dampening neural activity rather than promoting it. The primary neurotransmitter responsible for this inhibition is GABA. When GABA binds to its receptors, especially the GABA-A type, chloride channels open and chloride ions flow into the neuron. This makes the inside of the cell more negative (hyperpolarization), moving the membrane potential away from the threshold for firing an action potential and thus reducing the likelihood of neuronal firing. GABA-B receptors contribute to inhibition too, but in a slower, longer-lasting way by influencing potassium channels and calcium passage. In contrast, glutamate is the main excitatory transmitter, typically depolarizing neurons through AMPA and NMDA receptors and increasing the chance of firing. Serotonin and norepinephrine act as neuromodulators that can be either excitatory or inhibitory depending on the receptor subtype and circuit, but they are not the brain’s primary inhibitory signal. Clinically, many sedatives and anxiolytics work by enhancing GABA signaling, underscoring its central role in inhibitory control of brain activity.

Inhibitory signaling in the brain centers on dampening neural activity rather than promoting it. The primary neurotransmitter responsible for this inhibition is GABA. When GABA binds to its receptors, especially the GABA-A type, chloride channels open and chloride ions flow into the neuron. This makes the inside of the cell more negative (hyperpolarization), moving the membrane potential away from the threshold for firing an action potential and thus reducing the likelihood of neuronal firing. GABA-B receptors contribute to inhibition too, but in a slower, longer-lasting way by influencing potassium channels and calcium passage.

In contrast, glutamate is the main excitatory transmitter, typically depolarizing neurons through AMPA and NMDA receptors and increasing the chance of firing. Serotonin and norepinephrine act as neuromodulators that can be either excitatory or inhibitory depending on the receptor subtype and circuit, but they are not the brain’s primary inhibitory signal. Clinically, many sedatives and anxiolytics work by enhancing GABA signaling, underscoring its central role in inhibitory control of brain activity.