The strychnine-sensitive glycine receptor is the principal mediator of fast inhibitory synaptic transmission in the mammalian spinal cord and brain stem. As a member of the ligand-gated ion-channel family, it shares structural homology with the nicotinic acetylcholine, GABA(A/C) and serotonin 5-HT(3) receptors. Ion-channel activation and desensitisation are controlled by a variety of factors such as subunit composition, posttranslational modification, absence or presence of modulatory ions or other agents and possibly protein-protein interactions. Glycine-receptor mutations, either associated with the human motor disorder hyperekplexia or artificially introduced, have helped to define the regulatory domains of the receptor protein. In addition to their effects on glycine-receptor function, allelic variants of glycine-receptor genes may also affect biogenesis, assembly and degradation of the receptor.