Which neurotransmitter primarily has inhibitory effects, slowing neural activity?

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

Answer: (A)

Neural activity can be slowed by inhibitory signaling that makes neurons less likely to fire. GABA is the primary inhibitory neurotransmitter in the brain. It mainly acts through GABA-A receptors, which are ion channels that allow chloride ions to enter the neuron, hyperpolarizing it and lowering the likelihood of reaching the threshold for an action potential. There’s also GABA-B, a metabotropic receptor that reduces excitability by affecting ion channels more indirectly. This strong, rapid inhibition is what slows neural activity.

Norepinephrine, dopamine, and serotonin typically promote arousal, motivation, mood, or other modulatory effects, and their actions can be excitatory or context-dependent depending on the receptor involved. They aren’t primarily inhibitory like GABA.