The “relaxing factor” in blood vessels
In 1980, a pharmacologist noticed an experiment only worked when a thin layer of cells was left intact. It led to a Nobel Prize and, eventually, to the best-known ED pill.
The short version
- Robert Furchgott found that blood vessels only relaxed if their inner lining was intact.
- That lining was releasing a signal. It turned out to be nitric oxide, a gas.
- The discovery won the 1998 Nobel Prize and explains how most of this site’s tips work.
The accidental clue
In 1980, Robert Furchgott and John Zawadzki reported that a drug called acetylcholine relaxed strips of artery in the lab, but only if the inner lining (the endothelium) was left on. Without it, the same drug did nothing or made the vessel tighten. The lining had to be sending some signal to the muscle. They called it endothelium-derived relaxing factor.
Finding out what it was
Several labs chased the mystery signal through the 1980s. Ferid Murad had already shown that nitroglycerin, used for chest pain since the 1800s, works by releasing nitric oxide. Louis Ignarro and Furchgott then showed the relaxing factor was nitric oxide itself. Before this, nitric oxide was known mostly as an air pollutant.
The Nobel Prize
Furchgott, Ignarro, and Murad shared the 1998 Nobel Prize in Physiology or Medicine for discovering nitric oxide as a signaling molecule in the cardiovascular system.
What it led to
The same year, the first ED pill went on sale. It works on the nitric oxide pathway, keeping the signal active longer in the penis. The discovery also explains why leafy greens, exercise, and cocoa flavanols show up in circulation research: each seems to support nitric oxide in some way. See dietary nitrates.
Sources
Educational information, not medical advice. Read our medical disclaimer.