Glycine as a Neurotransmitter

Abstract

Glycine serves as a major inhibitory neurotransmitter in the adult vertebrate central nervous system and is implicated in the control of many motor and sensory pathways. In addition, this amino acid functions as an excitatory transmitter during embryonic development and is an essential coagonist at glutamatergic synapses containing the N‐methyl‐d‐aspartate (NMDA) subtype of glutamate receptors.

Keywords: amino acid transmitter; glycine transport; glycine receptor; strychnine antagonism; inherited motor disorder

Figure 1.

Inhibitory and excitatory actions of glycine depend on the direction of glycine receptor (GlyR)‐mediated Cl flux. (a) In adult neurons, opening of GlyR channels causes Cl influx into the cytoplasm of the depolarized cell, due to a low concentration of intracellular Cl. This results in charge neutralization of intracellular Na+ ions, and thus inhibition of neuronal firing. (b) Owing to the high activity of a specific chloride exchange system, embryonic neurons contain a high concentration of intracellular Cl. Opening of the GlyR channel therefore leads to Cl efflux, and thereby an increase of intracellular positive charge, i.e. neuronal excitation.

Figure 2.

Chemical structures of natural inhibitory amino acids and strychnine. Left, the glycine receptor agonists glycine, ã‐alanine and taurine as well as γ‐aminobutyric acid (GABA) are shown. Note different distances between positively and negatively charged head groups. Right, structure of strychnine. The aromatic ring positions indicated by arrows can be substituted without losing toxicity; this has been exploited for affinity purification and the synthesis of fluorescent derivatives.

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Further Reading

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How to Cite close
Betz, Heinrich, and Harvey, Robert J(Apr 2001) Glycine as a Neurotransmitter. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1038/npg.els.0000140]