Amino Acid Transport in Isolated Neurons and Glia
Glial cells, particularly astroglia, are thought to play an essential role in regulating the levels of many components in the extracellular space of the central nervous system 59. Changes in extracellular potassium concentration which accompany neuronal cell activity for example, have been shown to trigger a number of activities, such as uptake of potassium chloride and water into astroglia during simultaneous increase in glial cell oxygen consumption22. Thus a tight coupling of neuronal firing with glial supportive activity has been suggested on the basis of work done in the fields of ultrastructure, neurophysiology and biochemistry. Closely connected with water and ion fluxes is the transport of amino acids into and within the central nervous system. The microdistribution of amino acids may well influence the composition of brain proteins. A different aspect concerns the so-called transmitter amino acids, namely, γ-aminobutyric acid (GABA), glutamate, aspartate, glycine, taurine, etc., in which case amino acid transport may influence more directly neuronal electrical activity. Virtually all interest to date has been directed toward nerve-endings as regulators of extracellular transmitter amino acid levels through reuptake in analogy with amine transmitter systems 26, 28, 29. But during the last few years increasing evidence has appeared through widely different approaches that astroglial cells may be important regulators of transmitter amino acid uptake, release and metabolism 11,19,24,25,27.
KeywordsGlial Cell Dorsal Root Ganglion Glutamine Synthetase Amino Acid Transport Amino Acid Uptake
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