Which neurotransmitter is primarily associated with inhibitory effects and slowing neural communication?

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

Answer: (C)

GABA is the main inhibitory neurotransmitter in the brain, and its role is to slow neural communication by reducing the likelihood that neurons will fire. When GABA binds to GABA_A receptors, chloride ions rush into the neuron, hyperpolarizing it and making it harder to reach the firing threshold. GABA_B receptors produce slower, longer-lasting inhibition through different signaling pathways that also dampen neuronal activity. This inhibitory action helps balance excitatory signals (like glutamate) and keeps neural circuits from becoming overactive, which is important for processes such as anxiety regulation, motor control, and sleep.

Norepinephrine, dopamine, and serotonin influence arousal, motivation, mood, and other functions and can be excitatory or modulatory depending on the receptor and brain region, but they are not primarily associated with the fast, pervasive inhibition that slows neural signaling like GABA.