Serotonin
Serotonin is a chemical messenger made by the body that helps cells communicate. It acts in the brain and throughout the body, where its effects depend on the receptors it reaches. Also called 5-HT, it is involved in processes such as digestion, sleep, mood, and blood vessel activity.
- Also called
- 5-HT or 5-hydroxytryptamine
- Made from
- The amino acid tryptophan
- Where found
- Brain, gut, and other tissues
- Receptors
- Several families across the body
- Mushroom link
- Psilocin interacts with some receptors
What is serotonin?
Serotonin is a molecule that carries messages between cells. In the nervous system, it is a neurotransmitter: a chemical released by one nerve cell that can influence another. Its effects vary with the receiving cell and the receptor involved, so serotonin does not have one simple job or produce one universal feeling.
The body makes serotonin from tryptophan, an amino acid found in food. Serotonin is also known as 5-hydroxytryptamine, often shortened to 5-HT. It belongs to a broad group of signaling chemicals called monoamines. Although it is often discussed as a brain chemical, most of the body's supply is made in the digestive tract rather than the brain.
- 1Start with tryptophan
Cells use the amino acid tryptophan as the starting material.
- 2Make 5-HTP
An enzyme changes tryptophan into the intermediate 5-hydroxytryptophan.
- 3Form serotonin
A second enzyme converts 5-HTP into serotonin.
- 4Send a message
Cells release serotonin, which can bind to matching receptors.
- 5Clear the signal
Transporters take serotonin back up, or enzymes break it down.
How does serotonin work?
A serotonin-producing cell makes the molecule from tryptophan in two main steps. First, an enzyme converts tryptophan into 5-hydroxytryptophan, or 5-HTP. Another enzyme then converts 5-HTP into serotonin. Cells can store serotonin and release it when they send a signal; the molecule then binds to compatible receptors on nearby or distant cells.
There are multiple serotonin receptor types. Most work through internal signaling pathways, while one major family, called 5-HT3, acts as an ion channel. After signaling, serotonin can be taken back into cells by transporters or broken down, mainly into a substance called 5-HIAA. These steps help regulate how long and where its message has an effect.
Serotonin acts in the brain and peripheral tissues; most is outside the brain.
Serotonin signals through several receptor families with different effects.
Serotonin is a body messenger; psilocin is a separate mushroom-related compound.
Editorial placement to help compare; not a measurement.
Why does serotonin matter, and where is it found?
Serotonin participates in a range of body processes, including digestion, sleep, appetite, learning, and blood vessel activity. Its role depends on the tissue and receptor, which is why a message in the gut may have a different effect from one in the brain. Blood platelets also take up serotonin and can release it during clotting, where it influences nearby blood vessels.
Most serotonin is produced by specialized cells in the gastrointestinal tract, where it helps regulate gut activity. Smaller amounts are made in the brain, including in areas of the brainstem called the raphe nuclei, as well as in some other tissues. Serotonin in the blood does not simply cross into the brain, so the body's gut and brain serotonin systems are not one shared pool.
| Serotonin | Psilocin | Dopamine | |
|---|---|---|---|
| Molecule type | Natural body messenger | Psychoactive tryptamine | Natural body messenger |
| Made from | Tryptophan | Psilocybin conversion | Tyrosine |
| Receptor link | Several 5-HT receptors | Includes 5-HT2A | Dopamine receptor families |
| Mushroom link | Indirect research connection | Formed from psilocybin | Not psilocybin's primary link |
What are common misconceptions about serotonin?
Serotonin is sometimes nicknamed the “happiness chemical,” but that label leaves out its many roles and the complexity of brain signaling. A person's mood cannot be read from a simple serotonin level, and the idea that low serotonin alone causes depression is not supported by current scientific evidence. This does not mean serotonin is irrelevant; it means its relationship to mood is not a one-chemical explanation.
Serotonin is also not the same as psilocybin or psilocin. These are distinct molecules. Some medicines, including SSRIs, change how serotonin is reabsorbed by nerve cells, but that is not the same as adding serotonin or guaranteeing a particular emotional effect. Information about these substances is educational, not personal medical advice.
- 1935
Vittorio Erspamer reported a gut substance later identified as serotonin and called it enteramine.
- 1948
Researchers isolated serotonin from blood serum and gave it its now-familiar name.
- 1953
Researchers reported finding serotonin in the brain, broadening its study beyond the gut and blood.
How is serotonin connected to mushrooms?
The connection most often discussed in psychedelic science is through receptors. The body converts psilocybin into psilocin, a different molecule that can interact with serotonin receptors, especially the 5-HT2A receptor. This receptor activity is part of researchers' effort to understand how psilocin changes perception and other aspects of experience. It does not mean psilocin is serotonin or that the two substances act identically.
Research on psilocybin and serotonin receptors is ongoing, and findings about a molecule or receptor do not establish a guaranteed effect for an individual. Psilocybin is federally Schedule I in the United States. As of November 2026, Oregon and Colorado have state programs for supervised access, while New Mexico's medical program is being set up; laws and eligibility rules vary. Never eat a wild mushroom without expert identification.
Common questions about Serotonin
What does serotonin do?
Serotonin is a signaling molecule with different roles in different tissues. It is involved in processes that include digestion, sleep, appetite, learning, and blood vessel activity. Its effect depends on which cells receive the signal and which serotonin receptor is involved.
Is serotonin the same as psilocybin?
No. Serotonin is a molecule the body makes and uses for signaling. Psilocybin is a distinct compound found in some mushrooms; the body converts it into psilocin. Psilocin can interact with certain serotonin receptors, but it is not serotonin.
Does low serotonin cause depression?
The idea that low serotonin alone causes depression is not supported by current scientific evidence. Serotonin has many roles, and mood is influenced by complex biological and life factors. A simple serotonin level cannot explain a person's mood or diagnose a condition.
Is most serotonin in the brain?
No. Most of the body's serotonin is produced in the gastrointestinal tract, where it helps regulate gut activity. A smaller amount is made in the brain. Serotonin in the body and serotonin in the brain are not one freely shared supply.
Related terms
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Sources and further reading
Written by the Pscilly editorial team and reviewed November 2026. Educational content only, not medical or legal advice. Pscilly does not sell psilocybin. Never eat a wild mushroom without expert identification.