Serotonin (5-hydroxytryptamine, 5-HT) is a biogenic amine that functions as both a neurotransmitter and a hormone. It’s often called the "happiness hormone" or the "feel-good hormone," since it plays an important role in regulating mood, appetite, sleep, cognitive function, and social behavior.
Most serotonin (about 90%) is synthesized in enterochromaffin cells of the gastrointestinal tract, where it regulates gut motility. The rest is produced in the central nervous system, mainly in the raphe nuclei of the midbrain. Serotonin cannot cross the blood-brain barrier, so the peripheral and central pools of serotonin function independently of one another.
History of Discovery
The story of serotonin’s discovery is a fascinating scientific journey spanning several decades:
- 1935 — Italian pharmacologist Vittorio Erspamer discovered a substance in the lining of the gastrointestinal tract that caused smooth muscle to contract. He named it "enteramine."
- 1948 — American scientists Maurice Rapport, Arda Green, and Irvine Page isolated a vasoconstricting substance from blood serum and named it "serotonin" (from the Latin "serum" and "tonus," meaning tension).
- 1949 — Serotonin’s chemical structure was established: 5-hydroxytryptamine (5-HT).
- 1953 — Researchers proved that Erspamer’s "enteramine" and Rapport, Green, and Page’s "serotonin" were the same substance.
- 1957 — Dilworth Woolley and Eugene Shaw proposed a role for serotonin in mental illness, noting its structural similarity to the hallucinogen LSD.
- 1960s — Serotonin receptors were discovered in the central nervous system.
- 1970s — Scientists began to understand serotonin’s role in mood regulation and developed the first antidepressants targeting the serotonin system.
Research into serotonin has continued ever since, and today its many functions in the body, and its role in numerous physiological and pathological processes, are well documented.
Artificial Boosters and Ways to Raise Serotonin Levels
Pharmacological Agents
- Selective serotonin reuptake inhibitors (SSRIs) — antidepressants that block serotonin reuptake, raising its concentration in the synaptic gap. Examples: fluoxetine (Prozac), sertraline (Zoloft), paroxetine (Paxil), escitalopram (Lexapro).
- Monoamine oxidase inhibitors (MAOIs) — block the enzyme that breaks down serotonin. Examples: phenelzine, tranylcypromine.
- Tryptophan supplements — L-tryptophan is a precursor to serotonin, and taking it can boost serotonin synthesis.
- 5-HTP (5-hydroxytryptophan) — a direct precursor to serotonin, used as a dietary supplement.
Synthetic Serotonin Receptor Agonists
- Triptans — selective 5-HT1B/1D receptor agonists, used to treat migraines. Examples: sumatriptan, eletriptan.
- Buspirone — a partial 5-HT1A receptor agonist, used as an anti-anxiety medication.
- Psychedelic substances — LSD, psilocybin, and DMT are powerful serotonin receptor agonists, especially at 5-HT2A. Their potential for treating depression and PTSD is being actively studied.
Non-Pharmacological Ways to Raise Serotonin
While not "artificial boosters" in the strict sense, these methods promote a natural rise in serotonin levels:
- Physical activity — regular exercise stimulates serotonin production.
- Diet — a diet rich in tryptophan (dairy, nuts, poultry, eggs, legumes) can boost serotonin synthesis.
- Light therapy — exposure to bright light is used for seasonal affective disorder to increase serotonergic activity.
- Meditation and mindfulness — research suggests these practices can modulate the serotonin system.
Current Research
Serotonin remains an active area of scientific study. Of particular interest are:
- Serotonin’s role in the gut-brain axis and its effect on the microbiome
- New selective modulators of serotonin receptors for treating mental disorders
- The therapeutic potential of psychedelics acting through the serotonin system
- How the serotonin system interacts with other neurotransmitter systems
Understanding of serotonin’s complex mechanisms keeps expanding, opening new prospects for treating conditions ranging from depression to gastrointestinal disorders.