Links Between Nerves and Glands: The Story of Adrenaline

After the discovery of adrenaline, the rudimentary ideas of neurotransmission were developed in the 20-year period 18901910. It is entwined with the concept of neural transmission by humoral substances initiated in 1656 by Thomas Wharton and by Glisson, who associated the adrenal glands with nerve plexuses. How this linkage functioned was unknown until Claude Bernard showed that adrenal glands produced ‘secretions internes’ affecting the milieu intérieur. John Jacob Abel in 1899, and, independently, Jokichi Takamine in 1901, isolated a suprarenal extract that elevated blood pressure. Three years later Thomas Renton Elliott observed that from the adrenal medulla, a substance could be produced (i.e. adrenaline), whose effects resembled closely those of the sympathetic nervous system, thus echoing Wharton’s conclusions. In the 20th century. George Oliver, Edward Schäfer and Henry Dale were to clarify the physiology and show the way for clinical applications of adrenaline. So well known is adrenaline that the word has passed into common language as an inaccurate metaphor for a burst of anger, energy, or excitement. The discovery of adrenaline was entwined with the new but crucial concept of neural transmission by chemical (humoral) substances (Table 1). This discovery was the essential precursor of the modern neurotransmitter chemistry, necessary for the understanding of neural functions throughout the nervous system. First, the important historical background.