Glycine is an important inhibitory neurotransmitter in the mammalian central nervous system, especially in the brainstem and spinal cord. It acts by binding to anion-conducting glycine receptors that belong to a superfamily of ligand-gated ion channels. Glycine receptors were first purified as strychnine binding sites in membrane fractions of adult spinal cord from rats (1). These strychnine-sensitive binding sites are different from the strychnine-insensitive binding sites found in the N-methyl-D-aspartate (NMDA) subtype of glutamate receptors. Adult glycine receptors are heterodimers composed of two subunits of 48 kDa and 58 kDa, denoted as a1 and b subunits. Fetal glycine receptors are homomers composed of a2 subunits.
