Which neurotransmitter is known to be the most abundant inhibitory neurotransmitter?

GABA, or gamma-aminobutyric acid, is recognized as the most abundant inhibitory neurotransmitter in the brain. Its primary function is to reduce neuronal excitability throughout the nervous system. GABA achieves this by binding to specific receptors, primarily GABA-A and GABA-B, which facilitates the opening of ion channels that allow negatively charged ions, such as chloride, to enter the neuron. This influx results in hyperpolarization of the neuron, making it less likely to fire an action potential.

The inhibitory effects of GABA are crucial for maintaining the balance of excitation and inhibition within the brain, which is essential for proper functioning and preventing overstimulation. This neurotransmitter is involved in various physiological and psychological processes, including regulating muscle tone, promoting sleep, and modulating anxiety levels. Its importance is highlighted in various neurological and psychiatric conditions, where GABAergic dysfunction can lead to symptoms such as anxiety disorders, epilepsy, and mood disorders.

Other neurotransmitters in the choices provided have different primary functions; for instance, dopamine is involved primarily in reward and pleasure systems, serotonin plays a significant role in mood regulation, and norepinephrine is primarily involved in arousal and the body's fight-or-flight response.