GABA'S ROLE IN THE BRAIN. GABA is made in brain cells from glutamate, and functions as an inhibitory neurotransmitter meaning that it blocks nerve impulses. Glutamate acts as an excitatory neurotransmitter and when bound to adjacent cells encourages them to fire and send a nerve impulse.NTRODUCTION: Gamma-Amino Butyric acid (GABA) is an amino acid which acts as a neurotransmitter in the central nervous system. It inhibits nerve transmission in the brain, calming nervous activity. As a supplement it is sold and promoted for these neurotransmitter effects as a natural tranquilizer.