Otto Loewi (German: [ˈɔtoː ˈløːvi] ⓘ; 3 June 1873 – 25 December 1961)[4] was a German-born pharmacologist and psychobiologist who discovered the role of acetylcholine as an endogenous neurotransmitter.

For this discovery, he was awarded the Nobel Prize in Physiology or Medicine in 1936, which he shared with Sir Henry Dale, who was a lifelong friend that helped to inspire the neurotransmitter experiment.

He went to study medicine at the University of Strasbourg, Germany (now part of France) in 1891, where he attended courses by famous professors Gustav Schwalbe, Oswald Schmiedeberg, and Bernhard Naunyn among others.

Soon, however, after seeing the high mortality in countless cases of far-advanced tuberculosis and pneumonia, left without any treatment because of lack of therapy, he decided to drop his intention to become a clinician and instead to carry out research in basic medical science, in particular pharmacology.

As a result of his work on the action of phlorhizin, a glucoside provoking glycosuria, and another one on nuclein metabolism in man, he was appointed «Privatdozent» (lecturer) in 1900.

After being arrested, along with two of his sons, on the night of the German invasion of Austria, March 11, 1938, Loewi was released after three months on condition that he "voluntarily" relinquish all his possessions, including his research, to the Nazis.

He arrived to Britain in September 1938 and shortly afterwards he was offered a visiting professorship at the Université libre de Bruxelles via the Francqui Foundation.

[9] After teaching one semester in the first half of 1939 and going on vacation in England he didn't return to Brussels in September due to the outbreak of World War II.

Shortly after Loewi's death in late 1961, his youngest son bestowed the gold Nobel medal on the Royal Society in London.

The original of the bust is at the Marine Biological Laboratory in Woods Hole, Massachusetts, Loewi's summer home from his arrival in the US until his death.

Loewi's investigations "On an augmentation of adrenaline release by cocaine" and "On the connection between digitalis and the action of calcium" stimulated a considerable body of research in the years following their publication.

Thirteen years later, Loewi was awarded the Nobel Prize in Physiology or Medicine, which he shared with Sir Henry Hallett Dale.

[12][13] Loewi observed that by removing the pancreas from dogs, it gave them an experimental form of diabetes, which led to a change of the response of the eye to adrenaline.

[17] The mechanism of action of this phenomenon is unclear, but has been attributed to "a functional toxic disturbance of the sympathetic post-ganglionic neuron innervating the iris".