The glycine receptor (GLR) is a ligand-gated ion channel. It is functional as a heteropentamer, consisting of alpha (GLRA) and beta (GLRB) subunits. With no ligand bound, the receptor complex is closed to chloride ions. Binding of the inhibitory neurotransmitter glycine (Gly) to this receptor complex increases chloride conductance into neurons and thus produces hyperpolarization (inhibition of neuronal firing) (Grenningloh et al. 1990, Nikolic et al. 1998, Handford et al. 1996).