A recent experimental animal study showed that while nitric oxide is involved in initiation of periorbital allodynia and vasodilatation induced by exposure to glyceryl nitrate, a well-known migraine trigger, only vasodilatation was shown to be maintained by a direct nitric oxide action, whereas maintenance of allodynia proved to be a neuronal event mediated by TRPA1 activation and ensuing oxidative stress [109]. The gene discussed is TRPA1; the disease is migraine disorder.