Skip to Main Content

We have a new app!

Take the Access library with you wherever you go—easy access to books, videos, images, podcasts, personalized features, and more.

Download the Access App here: iOS and Android


5-Hydroxytryptamine (5HT, serotonin) and dopamine (DA) are neurotransmitters in the central nervous system (CNS) that also have prominent peripheral actions. Although high concentrations of 5HT are present in the CNS, about 95% of all 5HT in the human body is located in the periphery, with high levels in enterochromaffin cells throughout the gastrointestinal (GI) tract and in storage granules in platelets. The highest concentrations of DA are found in the brain, but DA stores are also present peripherally in the adrenal medulla, in the plexuses of the GI tract, and in the enteric nervous system. Fourteen mammalian 5HT receptor subtypes, categorized into seven subfamilies, and five DA receptor subtypes, categorized into two subfamilies, have been delineated by structural and pharmacological analyses and are encoded by separate genes. For some receptors, alternative RNA splicing or editing creates additional heterogeneity; for example, over 30 isoforms of the 5HT2C receptor subtype arise from RNA editing. The identification of individual receptor subtypes has facilitated development of subtype-selective drugs and elucidation of actions of 5HT and DA at a molecular level. Increasingly, therapeutic goals are being achieved by using drugs that selectively target one or more of the subtypes of 5HT or DA receptors or that act on a combination of both 5HT and DA receptors.



AADC: aromatic L-amino acid decarboxylase

ADHD: attention-deficit/hyperactivity disorder

BBB: blood-brain barrier

COMT: catechol-O-methyl transferase

CGRP: calcitonin gene-related peptide

CSF: cerebrospinal fluid

DA: dopamine

DAG: diacylglycerol

DAT: dopamine transporter

L-DOPA: 3,4-dihydroxyphenylalanine

DOPAC: 3,4-dihydroxyphenylacetic acid

EPI: epinephrine

EPS: extrapyramidal symptoms

GABA: γ-aminobutyric acid

GI: gastrointestinal

GPCR: G protein-coupled receptor

GSK-3: glycogen synthase kinase 3

5-HIAA: 5-hydroxyindole acetic acid

HSDD: hypoactive sexual desire disorder

5HT: 5-hydroxytryptamine, serotonin

HVA: homovanillic acid

LSD: lysergic acid diethylamide

MAO: monoamine oxidase

MPP+: 1-methyl-4-phenylpyridinium

MPTP: 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine

MSAA: multifunctional serotonin agonists and antagonists

NE: norepinephrine

NET: norepinephrine transporter

NO: nitric oxide

NSAID: nonsteroidal anti-inflammatory drug

NSS: neurotransmitter–sodium symporter

6-OHDA: 6-hydroxydopamine

PD: Parkinson's disease

PFC: prefrontal cortex

PKC: protein kinase C

PLC: phospholipase C

RLS: restless leg syndrome

SERT: serotonin transporter

SNRI: serotonin-norepinephrine reuptake inhibitor

SSRI: selective serotonin reuptake inhibitor

TAAR1: trace amine-associated receptor 1

TCA: tricyclic antidepressants

VMAT2: vesicular monoamine transporter 2

VNTR: variable number of tandem repeat



In the 1930s, Vittorio Erspamer began to study the distribution of enterochromaffin cells, which were stained with a reagent for indoles. The highest concentrations of these cells were found in GI mucosa, followed by platelets and the CNS. Subsequently, Irving Page and colleagues at the Cleveland Clinic isolated and characterized a vasoconstrictor substance released from platelets in clotting blood. This substance, named serotonin by Page, was identical to the indole, enteramine, isolated by Erspamer. Both enteramine and serotonin proved to be 5-hydroxytryptamine. Subsequent discovery of the biosynthetic and degradative pathways for 5HT and clinical presentation of patients with carcinoid tumors of intestinal enterochromaffin ...

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.