A widely distributed chemical substance (a monoamine), particularly found in the blood, brain, and certain cells of the gut; it is also known as 5-hydroxytryptamine (5-HT). It is synthesized from the amino acid tryptophan, plays an important part in haemostasis, and probably also acts as a neurotransmitter in the central nervous system. It is involved in sleep, emotional disposition (mood), prolactin secretion, and circadian rhythms.
| Serotonin | |
|---|---|
| Chemical name |
5-Hydroxytryptamine or 3-(2-aminoethyl)-1H-indol-5-ol |
| Chemical formula | N2OC10H12 |
| Molecular mass | 176.2182 g/mol |
| Monoisotopic mass | 176.0950 g/mol |
| Composition (weight) |
N: 15.8970% O: 9.0793% C: 68.1598% H: 6.8638% |
| CAS number | 50-67-9 |
| SMILES | NCCC1=CNC2=C1C=C(O)C=C2 |
| IUPAC InChI ID |
1/C10H12N2O/c11-4-3-7-6-12-10-2-1- 8(13)5-9(7)10/h1-2,5-6,12-13H,3-4,11H2 |
Serotonin (5-hydroxytryptamine, or 5-HT) is a monoamine neurotransmitter synthesized in serotonergic neurons in the central nervous system (CNS) and enterochromaffin cells in the gastrointestinal tract.
Explanation
In the central nervous system, serotonin is believed to play an important role in the regulation of body temperature, mood, sleep, emesis (vomiting), sexuality and appetite. If neurons of the brainstem that make serotonin- serotonergic neurons- are abnormal, there is a risk of sudden infant death syndrome, or SIDS, in an infant.
Biochemistry
Serotonin is found extensively in the human gastrointestinal tract (about 90% ), as well as in the blood stream.
In the body, serotonin is synthesized from the amino acid tryptophan by a short metabolic pathway consisting of two enzymes — Tryptophan hydroxylase (TPH) and Amino acid decarboxylase (DDC).
The gut secretes over 95% of the body's serotonin.
Serotonin taken orally does not pass into the serotonergic pathways of the central nervous system because it does not cross the blood-brain barrier.
One product of serotonin breakdown is 5-hydroxyindoleacetic acid (5 HIAA) which is excreted in the urine.
Neurotransmission
The neurons of the Raphe nuclei are the principal source of 5-HT release.
Serotonergic action is terminated primarily via uptake of 5-HT from the synapse. Various agents can inhibit 5-HT reuptake including MDMA (ecstasy), cocaine, tricyclic antidepressants (TCAs) and selective serotonin reuptake inhibitors (SSRIs).
Recent research suggests that serotonin plays an important role in liver regeneration and acts as a mitogen (induces cell division) throughout the body.
Pharmacology
The pharmacology of 5-HT is extremely complex, with its actions being mediated by a large and diverse range of 5-HT receptors.
One way of understanding it is through the use of MDMA (ecstasy), which is thought to cause a massive release of 5-HT, possibly by drawing it back through the transporter. MDEA, a closely related drug, appears to be purely a serotonin releasing agent, and lacks the strong stimulant effect of MDMA.) MDMA has also been shown to alleviate the symptoms of Parkinson's Disease, though this effect is thought to be mediated by its secondary effects on dopamine release, rather than serotonin itself.
5-HT receptors are also used by other psychoactive drugs, including LSD, DMT, and psilocybin, the active ingredient in psychedelic mushrooms.
Modulating levels
A variety of psychiatric medications affect serotonin levels, including the monoamine oxidase inhibitors (MAOIs), tricyclic antidepressants (TCAs), atypical antipsychotics, and the selective serotonin reuptake inhibitors (SSRIs).
Antidepressants
The MAOIs prevent the breakdown of monoamine neurotransmitters (including serotonin), and therefore increase concentrations of the neurotransmitter in the brain.
Some drugs inhibit this re-uptake of serotonin, again making it stay in the synapse longer. The newer Selective Serotonin Re-uptake Inhibitors (SSRIs) have fewer (though still numerous) side effects and fewer interactions with other drugs.
Recent research conducted at Rockefeller University shows that in both patients who suffer from depression and in mice that model that disease, levels of the p11 protein are decreased.
Serotonin syndrome
Extremely high levels of serotonin can have toxic and potentially fatal effects, causing a condition known as serotonin syndrome.
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