The structure and the ligand-binding site of the GABAC receptor [41]. CACA, cis-4-aminocrotonic acid; GABA, gamma-aminobutyric acid; ρ1–5, GABAC ρ subunits 1–5; TPMPA, (1,2,5,6-tetrahydropyridin-4-yl) methylphosphinic acid.