Aminobutyric acid
γ-Aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the mammalian brain where it acts at GABAA receptors, which are ligand-gated chloride channels. The GABAA receptor is generally pentameric. Its five subunits are alpha, beta, gamma, delta, and rho. The GABRD gene encodes the delta subunit. Specifically, the δ-subunit is usually expressed in GABAA receptors associated with extrasynaptic activity. The most common GABAA receptors have the gamma subunit, which allows the receptor to bind benzodiazepines. For this reason, receptors containing δ-subunits are sometimes referred to as “benzodiazepine-insensitive” GABAA receptors. However, they do show an exquisitely high sensitivity to ethanol compared to the benzodiazepine-sensitive receptors, which do not respond to ethanol. The δ-subunit containing receptors are also known to be involved in the ventral tegmental area (VTA) pathway in the brain's hippocampus, which means that they may have implications in learning, memory, and reward.