In 1998, the Nobel Prize in physiology or Medicine was awarded jointly to Robert F. Furchgott, Louis J. Ignarro and Ferid Murad for their discoveries concerning nitric oxide as a signaling molecule in the cardiovascular system.
Nitric oxide is a gas that transmits signals in the organism.
Signal transmission by a gas that is produced by one cell, penetrates through membranes and regulates the function of another cell represented an entirely new principle for signaling in biological systems. It was a sensation that this simple, common air pollutant, which is formed when nitrogen burns, for instance in automobile exhaust fumes, could exert important functions in the organism. It was particularly surprising since nitric oxide is totally different from any other known signal molecule and so unstable that it converted to nitrate and nitrite within 10 seconds. Nitric oxide was known to be produced in bacteria but this simple molecule was not expected to be important in higher animals such as mammals. Further research rapidly confirmed that nitric oxide is a signal molecule of key importance for the cardiovascular system and it was also found to exert a series of other functions.