Otto Loewi (June 3, 1873 - December 25, 1961) was a German-American pharmacologist, often called the "Father of Neuroscience." His first studies were in the field of metabolism where he proved that animals are able to rebuild their proteins from their degradation products, the amino acids, an essential discovery with regard to nutrition. He investigated how vital organs respond to chemical and electrical stimulation. He also established their relative dependence on epinephrine for proper function. Consequently, he learnt how nerve impulses are transmitted by chemical messengers. The first chemical neurotransmitter that he identified was acetylcholine. For this discovery he was awarded the Nobel Prize in Physiology or Medicine in 1936 which he shared with Henry Dale. When the Germans invaded Austria, in 1938, Loewi arrested and then released on condition that he voluntarily relinquish all his possessions to the Nazis. He moved to the US in 1940, where he became a research professor at the New York University College of Medicine. In 1946, he became a naturalized citizen of the United States. He died in 1961 at the age of 88.