Increased plasma nitrate stimulates the production of nitric oxide. Granule neurons have high levels of the neuronal isoform of nitric oxide synthase. Bacteria convert the added nitrite or nitrate to nitric oxide. Some phagocytes kill the ingested pathogen with oxidants and nitric oxide. Glutathione enhances the function of citrulline as part of the nitric oxide cycle. It is the precursor for the biosynthesis of nitric oxide. Substance P-induced vasodilatation is dependent on nitric oxide release. One of the main enzymatic targets of nitric oxide is guanylyl cyclase. The stability is reminiscent of the stability of nitric oxide and nitrogen dioxide. Upon mixing of concentrated hydrochloric acid and concentrated nitric acid, chemical reactions occur. Vallance performed studies which demonstrated the link between nitric oxide and blood pressure. Sildenafil (Viagra) is a common example of a drug that uses the nitric oxide pathway. This photon may have any of several different wavelengths characteristic of nitric oxide molecules. This may be due to an increase in the production of nitric oxide during exercise. They are converted into sulfuric acid and nitric acid.