Nitric oxide (NO), first identified as an endothelium-derived relaxation factor (EDRF), is now recognized as a regulator of many mammalian cells and tissue functions. It is synthesized via the oxidation of arginine by a family of nitric oxide synthases (NOS) which are either constitutive and calcium-dependent or inducible and calcium-independent. The endogenous production of NO plays a vital role in regulating physiological processes, e.g., blood vessel tone and neurotransmission, as well as in host defense and immunity. NO is a unique biological messenger molecule. Nitric oxide have physiological and pathophysiological roles in the nervous system. Nitric oxide may regulate neurotransmitter release, and it may play a key role in nervous system morphogenesis and synaptic plasticity and regulate gene expression. Under conditions of excessive formation, nitric oxide is emerging as an important neurotoxin in a variety of disorders of the nervous system. In addition, in many studies it has been found that nitric oxide plays a complex role in modulating the inflammatory response. [Journal of Turgut Ozal Medical Center 1997;4(4):453-461]
Key Words: Nitric oxide, nitric oxide synthase, NO, NOS, neurotoxin
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