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NIDA. (2019, August 26). Say What? "Serotonin". Retrieved from

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The NIDA Blog Team
August 26 2019
Serotonin molecule
Image by NIH. 

"Say What?" is a periodic series in which we define scientific terms and explain their importance.

Did you know that your brain is made up of 100 billion nerve cells called neurons? Neurons constantly exchange information between your brain and other parts of your body.

As neurons communicate with each other, they’re helped by a type of chemical called a neurotransmitter. When one part of your brain wants to communicate something to another part, it releases small amounts of neurotransmitters from one neuron to another.

Your body makes all kinds of neurotransmitters. One kind is called serotonin. It’s known as the “calming chemical” because its activity in certain brain circuits:

  • Lifts a person’s mood.
  • Eases tension and helps a person cope with stress.
  • Reduces anxiety and aggression.
  • Promotes sleep.
  • Affects appetite and memory.

Thanks to research funded by NIDA, scientists have learned that serotonin has another job. By attaching itself to a protein, serotonin can enter a cell’s nucleus and turn a gene on or off (this is called “gene expression”). That means that serotonin can help control how genes express themselves.

Serotonin’s ability to do this allows a cell to respond better to its changing environment. It helps a person’s personal biological “map” to develop as they grow, make choices, and are affected by outside influences like diet, lack of sleep, or drug use.

The newly discovered role of serotonin may increase our understanding of mood disorders and other psychiatric conditions like substance use disorders.

Learn more: Watch a short video about how your brain works