Biosynthesis of Epinephrine and Norepinephrine by Sympathetic Nerves and Ganglia

It is generally believed by the neurophysiologists that the sympathetic neurohormone is norepinephrine and not epinephrine as originally supposed. This concept of norepinephrine as the sympathetic neurohormone has evolved from much impressive circumstantial evidence; however, it has not been demonstrated that the biosynthesis of norepinephrine takes place in the sympathetic nerves and ganglia. This paper shows, through the use of labeled precursors, that the sympathetic nerves and ganglia synthesize norepinephrine in a systematic sequence from tyrosine and that this synthesis apparently terminates with norepinephrine rather than progressing to the formation of epinephrine.