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All About Serotonin

Serotonin is widely known as the happiness molecule and is known to regulate one's moods. However, serotonin also plays an important role in metabolism and other activities. Let's learn more about this molecule.

Site of production of serotonin

serotonin production in GI tract

Serotonin is a neuromodulator and can be synthesized in our body. It has been reported to regulate moods, metabolism, gut health, and clot formation. 90 % of serotonin is found in the gut and only 10 % is found in the central nervous system (CNS). In our brain, Raphe nuclei produce this molecule, and in the gastrointestinal tract, Enterochromaffin cells (ECs), produce this molecule.

Synthesis of serotonin

Serotonin is derived from the amino acid - tryptophan. Sleep regulating hormone, melatonin is also derived from tryptophan. Tryptophan is hydroxylated by the enzyme tryptophan hydroxylase to produce 5 hydroxy-tryptophan. This molecule when undergoes decarboxylation (removal of carboxyl from the core amino acid structure) results in the production of this neurotransmitter (5 hydroxy-trypamine). Various antidepressants work to upregulate this enzyme and target this metabolic pathway. Tryptophan hydroxylase is present at the site of synthesis. Tryptophan-rich food is an excellent way to increase serotonin levels naturally.

Transport of serotonin

Serotonin acts on the nervous system and needs to be transported from one place to another throughout the body. Platelets, the clot-forming cells in the body, are the carriers of these molecules. Hence, their action in blood clot formation has been studied and aroused the curiosity of researchers.

Working of serotonin

serotonin act on neurons

Serotonin acts on the nervous system by acting as stimulatory and inhibitory molecules. Nerve cells have serotonin receptors that bind to this molecule to create or alter the action potential working of the nerve. It has been observed that there are seven classes of these serotonin receptors and have been targeted to treat depression. One of the ways serotonin acts on nerve cells is when it's secreted by a nerve cell, it acts on the nerve cells in the vicinity. When serotonin binds with the receptor, it generates a signaling pathway. These molecules then separate from the receptor and return to the synthesizing neuron. One of the most popular drugs, Prozac works by stopping serotonin from entering back into the producing factory (neuron). This way, more serotonin is available in the environment, hence more of its effect can be observed.

When receptors fail to bind or interact with serotonin, it can have the same effect as no production of this molecule.

Gut microbes and serotonin

Gut microbes are the microbes that inhabit the gastrointestinal tract. This fauna inside the lumen of the digestive tract is important for the regulation of bodily functions. It is said to affect serotonin productivity. It has been reported that high serotonin levels help in the flourishing of good bacteria and vice versa.

Serotonin is a neurotransmitter that modulates mood functions. It also has effects on the sleep cycle and metabolism. The majority of serotonin is produced in the gastrointestinal tract, so trust your gut.


  • Gershon, M.D. (2013). 5-Hydroxytryptamine (serotonin) in the gastrointestinal tract. Current Opinion in Endocrinology & Diabetes and Obesity, 20(1), pp.14–21. doi:

  • Jones, L.A., Sun, E.W., Martin, A.M. and Keating, D.J. (2020). The ever-changing roles of serotonin. The International Journal of Biochemistry & Cell Biology, 125, p.105776. doi:

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