The 5-Hydroxyindole Pathway

From a study of the enterochromaffin cells (skin, intestinal mucosa) Erspamer S61) postulated the occurrence of a physiologically potent vascular hormone. From chemical and pharmacological studies it was concluded that this material, named enteramine, was an indole derivative carrying a phenolic group(s) and a side chain with a terminal primary or secondary amino group. 

Subsequently a compound with vasoconstrictor activity was isolated from serum by Rapport and co-workers S6S) and identified as 5-hydroxy-tryptamine. This compound was named serotonin. Enteramine and serotonin were soon shown to be one and the same substance. 

The exact physiological functions of serotonin are not known. It has been associated with gastrointestinal activity, nervous system function, kidney function, anaphylaxis, etc. 

The physiological and pharmacological properties of serotonin have been the subjects of recent reidews S6S, S 4)- 

Evidence that tryptophan is the precursor of serotonin has been amply demonstrated by isotopic tracer experiments (S6ff, 366). 

---

Chemistry, which has advanced our knowledge of the 5-hydroxyindole pathway of metabolism to such an extent, has established a few definite facts which are of great interest to the clinician. However, many of the most interesting suggestions and theories have not been able to stand up under careful chemical scrutiny. 

---