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. In the uterus, the function of the receptor appears to be related to tissue contractility. The binding of this pI subunit with other GABA(A) receptor subunits alters the sensitivity of recombinant receptors to modulatory agents such as pregnanolone (By similarity). Generally pentameric. There are five types of GABA(A) receptor chains: alpha, beta, gamma, delta, and epsilon. A sixth class of subunit: Rho form homomeric GABA receptors that do not appear to coexist with GABA(A) receptor subunits but with GABA(C) receptor subunits. Subunit Pi can also bind this complex (By similarity). Belongs to the ligand-gated ion channel (TC 1.A.9) family. Gamma-aminobutyric acid receptor (TC 1.A.9.5) subfamily. GABRP sub-subfamily.