Receptors for Amino Acids

Free amino acids in the central nervous system (eNS) serve as precursors for proteins, as sources of metabolic energy, and as neurotransmitters or neuromodulators. This diversity of function obscured their role as neuro­ transmitters for some time. It also confused the search by biochemists for specific receptors for amino acids that could play a role in synaptic function. Significant advances within the last decade have allowed the biochemical identification and partial characterization of several receptors for amino acid neurotransmitters. In this mini-review, I examine receptors for gam­ ma-aminobutyric acid (GABA), glycine, and glutamic acid. I discuss bio­ chemical, not neurophysiologic, approaches to their study. The reader is referred to other reviews for comprehensive treatments of amino acids as neurotransmitters (11, 34, 54, 58, 60, 66, 67) and of receptors for amino acids (58, 66).