GABA is a small-molecule neurotransmitter synthesized within the presynaptic terminal of GABA-containing neurons. Once synthesized, GABA is packaged in vesicles and stored at the post-synaptic terminal until the arrival of an action potential causes these vesicles to release their contents into the synaptic cleft. Once released, GABA molecules travel across the synapse to the post-synaptic membrane, where they are recognized by GABA receptors.