/ Thesaurus / 5 Synonyms of 5 hydroxytryptamine Find synonyms for: Noun1. serotonin, 5-hydroxytryptamine, monoamine neurotransmitterusage: a neurotransmitter involved in e.g. sleep and depression and memoryWordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: labyrinth Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language