[Nitric monoxide, a new neurotransmitter in the central nervous system].

Nitric oxide (NO) is a recently discovered endogenous molecule considered as an unconventional biological messenger. Experimental evidence indicates that, in the brain, NO is produced enzymatically (calcium-dependent mechanism) in response to stimulation of postsynaptic excitatory amino cid receptors. NO activates soluble guanylate cyclase, that results in increases of cGMP levels in target cells. NO is physiologically involved in synaptic plasticity mechanisms. In situation of excessive production, NO can exert neurotoxic effects, suggesting a role in neurodegenerative disorders, including post-ischemic damage.