Abstract
The free-radical gas nitric oxide (NO) recently has been identified as an important biological messenger molecule in both the central and peripheral nervous system. NO is generated by the enzyme NO synthase (NOS) by the oxidation of the amino acid L-arginine. As a dissolved gas, NO is an unusual neurotransmitter. It is not packaged in synaptic vesicles and released by exocytosis upon membrane depolarization, but rather diffuses from its site of production to surrounding neurons where it acts directly on specific intracellular targets. The activity of NO terminates when it chemically reacts with a target substrate. Although all of the targets of NO are not yet known, NO can bind to the iron associated with heme groups or result in nitrosylation of proteins, leading to conformational changes. One of the best-described targets of NO in the central nervous system is the heme-containing protein guanylyl cyclase. NO is a relatively long-lived free radical and does not react readily with most cellular components. This allows it to diffuse to several surrounding neurons and integrate neuronal activity on a local scale. NO is involved in a number of physiological processes including morphogenesis and synaptic plasticity. However, under conditions in which NOS is overstimulated, excessive formation of NO may mediate cell injury in a variety of disorders of the nervous system that result in neurodegeneration (1).
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References
Varner, P. D. and Beckman, J. S. (1995) Nitric oxide toxicity in neuronal injury and degeneration, in Nitric Oxide in the Nervous System (Vincent, S. R., ed.), Academic, New York, pp. 191ā206.
Bredt, D. S., Hwang, P. M., Glatt, C. E., Lowenstein, C, Reed, R. R., and Synder, S. H. (1991) Cloned and expressed nitric oxide synthase structurally resembles cytochrome P-450 reductase. Nature 351, 714ā718.
Southam, E. and Garthwaite, J. (1993) The nitric oxide-cyclic GMP signalling pathway in rat brain. Neuropharmacology 32, 1267ā1277.
Bredt, D. S., Hwang, P. M., and Synder, S. H. (1990) Localization of nitric oxide synthase indicating a neural role for nitric oxide. Nature 347, 768ā770.
Marietta, M. A. (1993) Nitric oxide synthase structure and mechanism. J. Biol. Chem. 268, 12,231ā12,234.
Bredt, D. S. and Snyder, S. H. (1989) Nitric oxide mediates glutamate-linked enhancement of cGMP levels in the cerebellum. Proc. Natl. Acad. Sci. USA 86, 9030ā9033.
Bredt, D. S. and Snyder, S. H. (1990) Isolation of nitric oxide synthetase, a calmodulin-requiring enzyme. Proc. Natl. Acad. Sci. USA 87, 682ā685.
Lowry, O. H., Rosebrough, N. J., Farr, A. J., and Randall, R. J. (1951) Protein measurement with the folin-phenol reagent. J. Biol. Chem. 193, 265ā275.
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Ā© 1999 Humana Press Inc., Totowa, NJ
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Ward, T.R., Mundy, W.R. (1999). Measurement of the Nitric Oxide Synthase Activity Using the Citrulline Assay. In: Harry, J., Tilson, H.A. (eds) Neurodegeneration Methods and Protocols. Methods in Molecular Medicineā¢, vol 22. Humana Press. https://doi.org/10.1385/0-89603-612-X:157
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DOI: https://doi.org/10.1385/0-89603-612-X:157
Publisher Name: Humana Press
Print ISBN: 978-0-89603-612-3
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