**3. Henry Hallett Dale: friend and colleague**

The other key player in the discovery of acetylcholine is Henry Hallett Dale who described acetylcholine as a neurochemical in 1914 [13]. In 1902 and subsequent years, Loewi visited the lab of Ernest Starling in London, England [12]. During those visits, he met Dale who, just like Loewi, was focused on biomedical bench work instead of clinical practice. Both became colleagues and lifelong friends. Dale's work included the isolation and identification of neurochemicals such as histamine and acetylcholine. He distinguished muscarinic and nicotinic acetylcholine activity which was instrumental for the later discovery of acetylcholine receptor classes and subtypes. Furthermore, based on the relatively transient effect of acetylcholine, Dale proposed the existence of an esterase that rapidly metabolized acetylcholine. Dale's findings laid the groundwork for Loewi's innovative discoveries. As a result of their cutting-edge and transformative research, 'the Nobel Prize in Physiology or Medicine 1936 was awarded jointly to Sir Henry Hallett Dale and Otto Loewi for their discoveries relating to chemical transmission of nerve impulses' [14]. Their work and discoveries were not without opposition in the field [15]. The famous neurophysiologist John Eccles believed that transmission at synapses was too fast to be carried out with

*Introductory Chapter: The Neurotransmitter Acetylcholine – A Young Centenarian DOI: http://dx.doi.org/10.5772/intechopen.112480*

chemicals. He thought that synaptic excitation had to be an electric process instead of a chemical one. The debate went on for several years in the middle of the 20th century. While Eccles initial idea was shown to be incorrect, he inadvertently helped Dale and others in the field to accomplish key experiments which proved chemical synaptic transmission in the peripheral and central nervous system. Eccles changed his opinion in the early 1950's after carrying out microelectrode experiments in his own lab. From then on, he was convinced of the existence of chemical synaptic transmission which he shared in a letter with Dale [5].
