Maurice M. Rapport pictured at the Albert Einstein College of Medicine.

The death has taken place of Maurice Rapport, a biochemist who helped isolate and name the neurotransmitter serotonin in the late 1940s.  Rapport’s work isolating this chemical which plays a key role in regulating mood, was revolutionary at a time when little was known about the way the brain functioned, and led to the creation of a wide variety of psychiatric and other drugs.

The New York Times, reporting on his death, outlined the background to his discovery.

Scientists had known since the 1860s of a substance in the serum released during clotting that constricts blood vessels by acting on the smooth muscles of the blood-vessel walls. In the 20th century, researchers pinpointed its source in blood platelets, but its identity remained a mystery.

Dr. Rapport, working with Dr. Page and Arda A. Green, isolated the substance and, in a paper published in 1948, gave it a name: serotonin, derived from “serum” and “tonic.”

On his own, Dr. Rapport identified the structure of serotonin as 5-hydroxytryptamine, or 5-HT, as it is called by pharmacologists. His findings, published in 1949, made it possible for commercial laboratories to synthesize serotonin and study its properties as a neurotransmitter.

More than 90,000 scientific papers have been published on 5-HT, and the Serotonin Club, a professional organization, regularly holds conferences to report on research in the field.

Maurice Rapport died on Aug. 18 in Durham, N.C. He was 91.