Masashi Yanagisawa (柳沢 正史, Yanagisawa Masashi, born May 25, 1960) is a Japanese-American molecular biologist and physician, famous for his discovery of the hormone endothelin and the neuropeptide orexin, the absence of which is the cause of narcolepsy.
Yanagisawa is most well known for his discovery of the hormone endothelin and the neuropeptide orexin. Early 1980s saw the revelation that nitric oxide was the substance endothelial cells produce to relax the smooth muscle around blood vessels, which causes vasodilation and increased blood flow.[10] This led to the speculation of and hunt for the inverse, an endothelium-derived vasoconstricting substance.[11] During his PhD study, Yanagisawa's supervisor, Tomoh Masaki, agreed to let him try to isolate the substance. This study became his PhD thesis, and he published his finding it 1988, naming the substance "endothelin" and reporting its peptide sequence.[12] He then published a number of reports on the function and regulation of endothelin, including working with Takeshi Sakurai to identify the receptor for endothelin.