Gamma-aminobutyric acid neurons (GABA)
GABA is synthesized by transforming glutamate into GABA via the glutamic acid decarboxylase enzyme. It is then stored in the axon for release. There are 2 different GABA receptors (A and B). The more common GABA-A is a ligand-gated chloride channel and the GABA-B is a G-protein linked receptor. These receptors can be further subtyped, but the functionality of the different subtypes has yet to
GABA produces its inhibitory response when it binds to the GABA-A receptor, causing a influx of chloride ion and decreasing the membrane potential further away from threshold (see graph). Several CNS-active drugs bind to this receptor and enhance GABA's binding effects.
The GABA-B receptor effects are much weaker than that of GABA-A.
There are relatively few GABA producing neurons, thus their influence is limited.
Extra info: GABA is released from a variety of neurons and as such has a wide distribution.
GABA-A and -B receptors can be found in the membranes of serotonin, norepinephrine and dopamine neurons.
Extra info: Not only is GABA released from a variety of neurons, but it can effect many different kinds.
GABA-B receptors increase the influx of calcium ions into the cell.
Extra info: The GABA-A receptor controls the influx of CHLORIDE into the cell.