γ-Aminobutyric acid (GABA), the principal inhibitory neurotransmitter in the vertebrate central nervous system (CNS) mediates fast synaptic transmission via ionotropic GABA(A) receptors. These receptors are pentameric assemblies of individual subunits arranged around a central, chloride-conducting pore. To date, 16 human GABA(A) receptor subunit genes have been characterized and grouped together according to their amino acid similarity and termed: α(1–6), β(1–3), δ(1–3), γ, ε, θ, and π¹. Each subunit has a large extracellular N-terminal domain, four hydrophobic membrane-spanning domains that form the channel region and a small extracellular C-terminus². These subunits can combine in many different ways to form functional receptors, but most synaptic receptors contain two α subunits (α 1–3 isoforms), two β subunits, and a γ subunit arranged in the order γ-β-α-β-α³.

The β1 subunit gene is located in the β1- α4- α2- γ1 gene cluster on chromosome 4, and is most highly expressed in the adult rat hippocampus⁴. GABA(A) R genes are postulated to play a role in neuronal maturation, synaptogenesis, and predisposition to neurological disease. Increases in GABA levels and changes in GABA(A) R subunit gene expression, including decreased β1 mRNA levels, have been observed in animal models of epilepsy⁵. Recent genetic studies have implicated GABA(A) β1 Receptor (GABRB1) in bipolar disorder, schizoaffective disorder and major depression⁶. In addition, GABRB1 is associated with the risk of alcohol dependence⁷.