Lionel Parra Iglesias 3D creation showing a schematic drawing of GABAA receptors and a GABAergic synaptic terminal (original 2D images from Maurice Garret).
Native GABAARs (top panel), which are heteropentameric structures containing α1, α2 or α3 with β and γ subunits, are located at the synapse (bottom panel) and mediate a phasic inhibitory effect. The aggregation of receptors on the postsynaptic domain depends on scaffolding proteins, including gephyrin. GABAARs containing the α5 or δ subunits are extra-synaptic with a high sensitivity to GABA and mediate tonic activity as a function of ambient transmitter level in the extracellular space. GABA levels depend on the expression of two isoforms of glutamate decarboxylase (GAD 67 and 65), the vesicular transporter VGAT, and the transporters GAT-1 and GAT-3.