Nitric oxide: a neural messenger.

Nitric oxide (NO) is a messenger molecule that is now a well established neurotransmitter in the central and peripheral nervous systems. NO was initially characterized as the "endothelium-derived relaxation factor" and subsequently found to mediate the elevation in cGMP following glutamatergic stimulation in the nervous system. Pharmacological and immunohistochemical data suggest numerous roles for NO throughout the body. NO knockout mice have demonstrated that NO is essential in behavioral and autonomic function. NO also appears to have neurotoxic and neuroprotective effects and may have a role in the pathogenesis of stroke and other neurodegenerative disorders.