GABA

GABA is the brain's main calming chemical messenger — the substance one nerve cell releases to tell its neighbors to quiet down. Brain cells, called neurons, talk to each other by squirting tiny puffs of chemicals across the narrow gap between them. Some of those chemicals shout “fire!” and others whisper “settle down,” and GABA is the most common whisper. Because so much of the brain runs on this one off switch, GABA is often described as the main inhibitory neurotransmitter, where inhibitory simply means firing-reducing and a neurotransmitter is any chemical neurons use to signal one another.

When GABA lands on a receiving neuron, it slots into a matching docking site called a receptor and nudges the cell further away from the threshold it must reach in order to fire its own electrical pulse. In effect, GABA raises the bar, so the neuron needs a stronger push before it will respond. This braking action keeps brain activity from running away into overexcitement: too little GABA is linked to anxiety, restlessness, and seizures, while many calming drugs — including alcohol, anti-anxiety medicines, and some sleep aids — work by boosting GABA's quieting effect. A healthy brain depends on a balance between GABA's brake and the main excitatory accelerator, a messenger called glutamate.