pargyline , a monoamine oxidase inhibitor , led to a marked increase in serotonin and a decrease of 5-hydroxyindoleacetic acid while p-chlorophenylalanine , by blocking the conversion of tryptophan to 5-hydroxytryptophan , selectively depleted 5-hydroxytryptophan , serotonin , and 5-hydroxyindoleacetic acid .
C0041249
tryptophan
C0000578
5-hydroxytryptophan