ABSTRACT
The glycine receptor is a member of the pentameric ligand-gated ion channel superfamily. Like GABA channels, it is permeable to anions and mediates hyperpolarizing synaptic inhibition in adult neurons. Glycinergic synaptic currents are faster than GABAergic ones and are most important in the sensory and motor circuits of the spinal cord. No metabotropic glycine receptors are known ,and only five subunits for the glycine ion channel are found in mammals, limiting the molecular diversity of this receptor. The adult synaptic receptor is α1β, and this type of receptor is localized to the synapse by binding to the scaffolding protein gephyrin.
There are few pharmacological tools: several amino acids such as β-alanine, alanine and serine activate this receptor, but the transmitter glycine is the most efficacious agonist. The receptor is blocked by the potent competitive antagonist strychnine, and by the pore blocker picrotoxin, which is more potent on homomeric channels. In man, loss-of-function mutations of the glycine receptor cause a rare channelopathy, startle disease or hyperekplexia. The relative simplicity of composition and high conductance make glycine receptors good subjects for molecular work to understand receptor activation in the superfamily by single-channel recording.
