Component of the heteropentameric receptor for GABA, the major inhibitory neurotransmitter in the vertebrate brain. Functions also as histamine receptor and mediates cellular responses to histamine (By similarity). Functions as receptor for diazepines and various anesthetics, such as pentobarbital; these are bound at a separate allosteric effector binding site. Functions as ligand-gated chloride channel. Heteropentamer, formed by a combination of alpha, beta, gamma, delta and rho chains. Binds UBQLN1. Interacts with KCTD8, KCTD12, KCTD12B and KCTD16; this interaction determines the pharmacology and kinetics of the receptor response, the KCTD proteins markedly accelerating the GABA-B response, although to different extents. Belongs to the ligand-gated ion channel (TC 1.A.9) family. Gamma-aminobutyric acid receptor (TC 1.A.9.5) subfamily. GABRB1 sub-subfamily.