The neurotransmitter GABA (γ-aminobutyric acid) inhibits the activity of signal-receiving neurons by interacting with the GABA_A receptor on these cells.¹ There are two major types of GABA receptors: the ionotropic GABA_A (GABA_A R) and the metabotropic GABA_B receptors.  

GABA_A R belongs to the ligand gated ion channel superfamily.^1,2 

It is a heteropentamer, with all of its five subunits contributing to the pore formation. To date, eight subunit isoforms were cloned: α, β, γ, δ, ε, π, θ, and ρ.¹

The native GABA_A receptor, in most cases, consists of 2α, 2β and 1γ subunit. Three γ subunits genes have been identified in mammals. 

The binding of GABA to its GABA_A receptor results in conformational changes that open a Cl^- channel, producing an increase in membrane conductance, resulting in inhibition of neural activity.^2,3 

Recently, a genetic linkage between familial epilepsy syndrome and mutations in the γ2 subunit of the GABA_A receptor have been demonstrated.^4,5