What neurotransmitter was discovered by Otto Loewi?

Otto Loewi's groundbreaking experiments led to the discovery of the neurotransmitter acetylcholine, which he identified as a chemical messenger that plays a crucial role in transmitting signals in the nervous system. In his famous 1921 experiment, Loewi stimulated the vagus nerve of a frog's heart, which caused a decrease in heart rate. He then collected the fluid from the heart and applied it to a second heart, which also slowed its rate, demonstrating that this effect was due to a chemical substance released in response to nerve stimulation. This chemical was later identified as acetylcholine, marking a pivotal moment in neuroscience and our understanding of synaptic transmission. This discovery not only emphasized the role of neurotransmitters in communication between neurons but also laid the groundwork for further research into the biochemical processes underlying nerve function.