GAD-65 and GAD-67, glutamate decarboxylases function to catalyze the production
of GABA (γ-aminobutyric acid). In the central nervous system GABA
functions as the main inhibitory transmitter by increasing a Cl-conductance
that inhibits neuronal firing. GABA has been shown to activate both ionotropic
(GABAA) and metabotropic (GABAB) receptors as well as a third class
of receptors called GABAC. Both GABAA and GABAC are ligand-gated ion
channels, however, they are structurally and functionally distinct. Members
of the GABAA receptor family include GABAA Rα1-6, GABAA R β1-3,
GABAA Rγ1-3, GABAA Rδ, GABAA Rε, GABAA Rρ1 and GABAA Rρ2. The
GABAB family is composed of GABAB R1α and GABAB R1β. GABA transporters
have also been identified and include GABA T-1, GABA T-2 and
GABA T-3 (also designated GAT-1, -2, and -3). The GABA transporters function
to terminate GABA action.