serotonin
serotonin
English (coined from serum + tonic + -in)
“Serotonin was discovered in blood serum, named for its ability to constrict blood vessels, and then found to do its most important work in a place nobody expected — the gut, not the brain.”
Serotonin was coined in 1948 by Maurice Rapport, Arda Green, and Irvine Page at the Cleveland Clinic. They isolated a substance from blood serum that caused smooth muscle to constrict — hence sero- (serum) + ton- (tone, tension) + -in (chemical suffix). The name describes its first observed function: a substance in serum that affects muscle tone. They had no idea they had found one of the most important neurotransmitters in the body.
The same molecule had been independently identified in the gut by Vittorio Erspamer in Italy, who called it 'enteramine' (amine of the intestine). When the two substances turned out to be identical, Rapport's name won. This turned out to be geographically appropriate: about 90 percent of the body's serotonin is produced in the gut, not the brain. The intestine was where it was first found, and the intestine is where most of it lives.
Serotonin's role in mood regulation was established in the 1960s and 1970s. The 'serotonin hypothesis' of depression — the idea that low serotonin levels cause depressive symptoms — became the basis for selective serotonin reuptake inhibitors (SSRIs), the most prescribed class of antidepressants worldwide. Prozac (fluoxetine), launched in 1987, was the first blockbuster SSRI. The hypothesis is now considered an oversimplification, but it shaped three decades of psychiatric treatment.
The serotonin system is involved in mood, sleep, appetite, digestion, bone density, and wound healing. It is not simply the 'happiness chemical,' despite persistent popular descriptions. The fact that most serotonin is in the gut, not the brain, hints at a connection between digestive health and mental health that researchers are still exploring. The word means 'serum toner.' The molecule does far more than tone serum.
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Today
SSRIs are prescribed to approximately 13 percent of American adults. Prozac, Zoloft, Lexapro, and their generics are among the most commonly used medications in the developed world. The serotonin hypothesis — low serotonin equals depression — has been challenged by research showing the relationship is more complex, but SSRIs remain effective treatments for many patients regardless of the mechanism.
Ninety percent of your serotonin is in your gut. The 'happiness chemical' lives in your intestines. The connection between what you eat and how you feel is not metaphorical — it is biochemical. The word means 'serum toner.' The molecule means something much stranger.
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