GABA-A receptors are ligand-gated anion channels formed by pentameric complexes including α, β, γ, δ, ε, π, and ρ subunits, and mediate fast synaptic inhibition in response to GABA (Cutting et al., 1991; Enoch, 2008). GABA binds to an extracellular ligand-binding domain, while 4 trans-membrane domains form the ion channel for chloride transportation into cells. The effects of drugs and alcohol on GABA neurotransmission have been extensively studied, as has their role in alcohol dependence (Barnard et al., 1998; Koob, 2006; Lobo and Harris, 2008; Vengeliene et al., 2008). The GABA-ρ1 receptor subunit was originally cloned based upon homology to the GABA-A receptor subunits, and when expressed encodes a GABA-responsive chloride channel that binds mucimol (Cutting et al., 1991). The closely-related ρ2 subunit was cloned by homology to ρ1 (Cutting et al., 1992). Sequence similarity makes them part of the GABA-A family of receptors, and they form ligand-gated chloride channels, but insensitivity of the homopentamers to baclofen and bicuculline as well as benzodiazepines lead them to also be classified as GABA-C receptors (Bormann, 2000; Kusama et al., 1993; Shimada et
