ChEBI: Nitric oxide is a nitrogen oxide which is a free radical, each molecule of which consists of one nitrogen and one oxygen atom. It has a role as a neurotransmitter, a signalling molecule, a vasodilator agent, a bronchodilator agent, a radical scavenger, a human metabolite, an Escherichia coli metabolite and a mouse metabolite. It is a nitrogen oxide, an inorganic radical and a member of reactive nitrogen species.