What impact does GABA have on neuronal excitability?

GABA, or gamma-aminobutyric acid, is a key neurotransmitter in the central nervous system known primarily for its inhibitory effects. When GABA binds to its receptors, it typically causes an influx of chloride ions into the neuron, making it more negatively charged. This hyperpolarization of the neuronal membrane reduces the likelihood of action potentials firing, thereby decreasing neuronal excitability.

The role of GABA as an inhibitory neurotransmitter is essential for maintaining the balance between excitation and inhibition within the brain. This balance is critical for normal functioning, including anxiety regulation, seizure control, and overall emotional stability. Increased GABA activity can lead to sedation and anxiolytic effects, which further illustrates its role in reducing neuronal excitability.

In contrast, the other choices suggest either enhancing excitability, having no effect, or causing overactivity, which do not accurately reflect the primary function of GABA in the nervous system. Therefore, the assertion that GABA reduces excitability is well-supported by its pharmacological and physiological roles in neuronal communication.