GABA, the major inhibitory neurotransmitter in the vertebrate brain, mediates neuronal inhibition by binding to the GABA/benzodiazepine receptor and opening an integral chloride channel. There are five types of GABA(A) receptor chains: alpha, beta, gamma, delta, and rho. GABA-A R rho 1 is a member of the rho subunit family and is highly expressed in the retina and in a lesser extent in brain, lung and thymus. GABA-A R rho 1 could play a role in retinal neurotransmission.