Serotonin is a neurotransmitter that is responsible for your happiness! Most anti-depressants focus on the production of serotonin.

Introduction:What is Serotonin?

Serotonin, also called  5-Hydroxytryptamine (5-HT), is a biochemical messenger and regulator, synthesized from the essential amino acid L-Tryptophan.

In humans, it is found primarily in the central nervous system, gastrointestinal tract, and blood platelets.

It mediates several important physiological functions including neurotransmission, gastrointestinal motility, hemostasis, and cardiovascular integrity (R).

Beneficial Effects of Serotonin

1) Serotonin Affects Heart Function


5-Hydroxytryptamine can be considered as a significant circulating hormonal factor implicated in normal cardiovascular function either by acting directly on heart cells or by stimulating chemosensitive nerves from the heart (R).

Patients with carcinoid tumors (rare slow growing cancers) have high levels of this regulator associated with arrhythmia, leading to heart block or to valvular fibroplasia (R).

Also, mouse embryos grown in the presence of either a high concentration of 5-Hydroxytryptamine or Serotonin-specific reuptake inhibitors show a decreased proliferation of myocardium, cardiac mesenchyme, and endothelium (R).

2) Serotonin Induces Intestinal secretions

In the gastrointestinal tract, 5-HT initiates responses like nausea, intestinal secretion, and peristalsis and has been implicated in gastroenteric diseases like irritable bowel syndrome (R).

The secretory effects of 5-HT are mediated through different receptors: It induces secretion across human ileal mucosa, whereas a receptor of the 5-HT2A subtype appears to mediate the effect in the human sigmoid colon (R).

3) Serotonin Helps Control Body Temperature and Breathing

5-HT-producing cells in the mouse brain play an essential role in maintaining a healthy balance in body temperature and breathing (R).

One study in rats (Tph2 knockout) suggests that 5-HTP is important to balancing the control systems for breathing and temperature during development (R).

Neurons in all of the nuclei that govern respiratory control have serotonin neurons (R).

4) Brain Serotonin Can Affect Your Mood


Acute tryptophan depletion (ATD) can result in lower mood and increase in irritability or aggressive responding.

Overall, studies manipulating tryptophan levels support the idea that low 5-Hydroxytryptamine levels can predispose subjects to mood and impulse control disorders.

Higher levels of 5-HT may help to promote more constructive social interactions by decreasing aggression and increasing dominance (R).

5) Serotonin Contracts Vascular Muscles

5-HT causes contraction of the vascular smooth muscle cells in most blood vessels studied in the lab (mainly due to the activation of S2-serotogenic receptors) (R).

The original intent of investigating 5-HT was for its vasoconstrictor effects. Early studies in dogs established a triphasic response to serotonin when injected intravenously (R).

  • An initial fall in blood pressure
  • A rise in blood pressure
  • Another fall in blood pressure

When released from activated platelets, 5-HT can induce vasoconstriction in most large arteries, large veins, and venules.

It can also indirectly contribute to vasoconstriction by amplifying the response of other vasoactive substances such as NET, angiotensin II, and histamine (R).

6) Serotonin May Impact Bone Regulation


5-HT receptors have been identified in all the major bone cell types (osteoblasts, osteocytes, and osteoclasts) (R).

Recent data suggest that gut-derived 5-Hydroxytryptamine may mediate the skeletal effects of LDL receptor-related protein 5.

Evidence suggests that SSRIs (Selective Serotonin Reuptake Inhibitors) are associated with reduced bone mass, increased bone loss, and increased risk of fractures (R).

Some studies suggest a direct stimulatory effect of 5-HT on bone formation pathways (R), whereas others have found inhibitory effects (R).

7) Serotonin Increases Hypertension

Early experiments with specific 5-HT receptor antagonists indicated that 5-HT1-like antagonism, as well as Serotonin antagonism, corrected hypertension in animal models (R).

Several mechanisms were proposed to explain this including direct vasodilation, inhibition of adrenergic input, and stimulation of central areas contributing to correction of vasomotor tone.

5-Hydroxytryptamine causes heart and lung tissue to replicate and grow (R,R,R).

In mice and people with high levels of 5-HT2B in the lungs is associated with the development of pulmonary hypertension (R,R).

8) Serotonin Affects Depression


Alterations in the serotogenic neuronal function in the central nervous system occur in patients with major depression, which can be evidenced by the reduced concentration of 5-HT in the postmortem brain tissue of the depressed.

In a pilot study in patients with major depression, alterations in 5-HT neurons showed to play a role in the cause of depression (R).

9) Serotonin Impacts Anorexia Nervosa

5-HTP is involved in almost all the behavioral changes observed in Anorexic patients.

Both genetic and environmental factors contribute toward Anorexia. It is suggested that tryptophan supplementation may help Anorexics (R).

Tryptophan is a precursor of serotonin and an essential amino acid only available in the diet, it is, therefore, likely that excessive diet restriction may lead to decreased brain 5-HT stores.

10) Serotonin Impacts Attention-Deficit Hyperactivity Disorder

In one controlled trial, families were studied to determine the link between the serotogenic system and Attention-Deficit Hyperactivity Disorder (ADHD). Preliminary data suggested an important role of the 5-HT system in the development of ADHD (R).

There is clear evidence that Dopamine and 5-Hydroxytryptamine neuronal systems interact in ADHD (R).

11) Serotonin Affects Carbohydrate-Craving And Obesity

5-HT-releasing brain neurons are unique in that the amount of neurotransmitter they release is normally controlled by food intake:

Carbohydrate consumption–acting via insulin secretion and the “plasma tryptophan ratio”–increases serotonin release; protein intake lacks this effect (R).

12) Serotonin May Play A Role In Kidney Activity


In kidney injury, tissue damage occurs and platelet activation is observed. Recent studies suggest that some factors, such as 5-Hydroxytryptamine, are released into microenvironment upon platelet activation following kidney injury (R).

Technical Section

  • Various agents can inhibit 5-HT reuptake, including cocaine, dextromethorphan (an antitussive), tricyclic antidepressants and selective serotonin reuptake inhibitors (SSRIs).
  • In animals including humans, 5-Hydroxytryptamine is synthesized from the amino acid L-tryptophan by a short metabolic pathway consisting of two enzymes: tryptophan hydroxylase and aromatic amino acid decarboxylase (R).
  • 5-HT is produced in two steps. The essential amino acid tryptophan is hydroxylated to 5-hydroxytryptophan (5-HTP) by tryptophan hydroxylase. In a second step, 5-HTP is decarboxylated to form 5-HT (R).

FDA Compliance

The information on this website has not been evaluated by the Food & Drug Administration or any other medical body. We do not aim to diagnose, treat, cure or prevent any illness or disease. Information is shared for educational purposes only. You must consult your doctor before acting on any content on this website, especially if you are pregnant, nursing, taking medication, or have a medical condition.


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  • William Preston

    Could 200mg serotonin daily cause any probems?

  • Lauren Cohn

    I have Lyme Disease and produce no serotonin. I was on 5-HYDROXYTRYPTAMINE HCL. I can no longer get it. I’m desperate to find it. Can you help me? I live in Los Angeles, CA.

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