Glial transporters for glutamate, glycine, and GABA III. Glycine transporters

Glial cells possess transport systems for the three major amino acid neurot ransmitters glutamate, gamma -aminobutyric acid (GABA) and glycine, involve d in the arrest of neurotransmission mediated by these compounds. Two glyci ne transporters have been cloned: GLYT1, mainly expressed by glial cells an d shown to colocalize with NMDA receptors, and GLYT2, exclusively expressed by neurons and colocalized with the inhibitory glycine receptors, The way in which the regulation of extracellular glycine concentration by glial gly cine transporters affects physiological and pathological conditions is disc ussed. The presence, differential pharmacology and specific regulation of g lycine transporters in glial cells strongly support an important role for g lia in the modulation of both, excitatory and inhibitory neurotransmission. (C) 2001 Wiley-Liss, Inc.