The involvement of serotonin (5-HT) in gastrointestinal (GI) physiology was recognized even before its structure had been discovered or anything was known about its role in the central nervous system. In 1937, Vittorio Erspamer extracted a factor, derived from the enterochromaffin (EC) cells of the GI epithelium, which he identified as an amine and called ‘enteramine’ (Erspamer, 1937). ‘Enteramine’ was unknown to Maurice Rapport when, in 1948, he isolated 5-HT as a serum vasoconstrictor and demonstrated its chemical structure (Rapport et al. 1948). 5-HT has thus been known to posterity as serotonin, not ‘enteramine’.