Gamma-aminobutyric acid receptor subunit beta-3 (GABAA Receptor, b3) is a receptor for gamma-aminobutyric acid (GABA), the major inhibitory neurotransmitter in the vertebrate brain. GABA mediates neuronal inhibition by binding to the GABA/benzodiazepine receptor and opening an integral chloride channel. The GABA receptor is pentameric in structure, and there are five types of GABA(A) receptor chains: alpha, beta, gamma, delta, and rho. Phosphorylation of serine 408 and serine 409 within the beta-3 subunit have been shown to be critical for the functional modulation of beta-3 containing recombinant receptors.