Serotonin is a neurotransmitter that helps regulate emotions and body functions such as sleep, sexual function, appetite, temperature regulation (and more).
It is also produced in the mind and can be heavily influenced by psychological factors. This article looks at this important chemical and how it works.
Serotonin and Mood Regulation: How Important Is It?
The link between serotonin and mood regulation has been extensively studied and is a key focus in neuroscience and mental health.
Serotonin acts as a chemical messenger, transmitting signals between nerve cells in the brain. It is synthesized from the essential amino acid tryptophan and stored in specialized cells called vesicles.
When released, the neurotransmitter binds to specific receptors, including the 5-HT2A receptor, modulating the activity of neurons and influencing various brain circuits involved in mood and emotional processing.
The exact mechanisms by which serotonin influences mood regulation are complex and poorly understood. However, it is believed that serotonin helps regulate the balance of other neurotransmitters involved in mood, such as dopamine and norepinephrine.
When serotonin binds to its receptors, it can have both inhibitory and excitatory effects on the activity of neurons. Through these effects, it helps regulate the balance of neurotransmitters in the brain, such as dopamine and norepinephrine, which are also involved in mood and emotions.
Serotonin’s interactions with these neurotransmitter systems contribute to its overall influence on mood and behavior. Additionally, it may play a role in neuroplasticity, the brain’s ability to adapt and rewire itself, which is crucial for maintaining emotional well-being.
The Role of Serotonin in the Digestion
Most serotonin in the body is found in the gastrointestinal (GI) tract, which helps regulate various digestive processes.
Within the digestive system, the neurotransmitter is primarily produced by enterochromaffin cells, a type of neuroendocrine cell found in the lining of the gastrointestinal tract. These cells release serotonin into the surrounding tissues, acting as a local signaling molecule.
One of the main functions of serotonin in the digestive system is to regulate gut motility or food movement through the digestive tract. It acts on receptors located on the smooth muscle cells in the walls of the intestines, stimulating contractions and promoting the rhythmic movement of food. This helps facilitate the efficient digestion and absorption of nutrients.
Serotonin also plays a role in regulating the secretion of fluids into the digestive system. It can stimulate the release of digestive juices, such as stomach acid and enzymes, which aid in the breakdown of food. Additionally, it can influence mucus secretion in the intestines, helping to lubricate and protect the intestinal lining.
Furthermore, serotonin is involved in regulating sensations in the digestive system. It can influence the perception of pain and sensations like nausea and vomiting. Changes in serotonin levels or signaling in the gut have been associated with conditions such as irritable bowel syndrome (IBS) and functional gastrointestinal disorders.
The regulation of gut motility and secretion by serotonin involves complex interactions between serotonin receptors, neural pathways, and other signaling molecules within the gut. For example, activating specific serotonin receptor subtypes can enhance or inhibit gut motility and secretion, depending on the specific context and location within the digestive system.
What Serotonin Has to Do With Cardiovascular Health
While serotonin is commonly associated with its effects on mood and emotions, it has important physiological functions in the cardiovascular system.
Serotonin is released from specialized cells called platelets, which are involved in blood clotting, and it acts as a vasoconstrictor, meaning it causes blood vessels to constrict or narrow.
When released, the neurotransmitter binds to receptors on the smooth muscle cells of blood vessel walls, leading to their contraction. This constriction reduces the diameter of blood vessels, increasing blood pressure.
In addition to its vasoconstrictive effects, serotonin also influences heart function and can stimulate the release of norepinephrine, another neurotransmitter that regulates heart rate and contractility. By enhancing the release of norepinephrine, serotonin can increase heart rate and strengthen the force of each heartbeat.
Serotonin regulation of blood pressure and heart function involves a complex interplay of various systems within the body. The release and actions of the neurotransmitter are tightly controlled to maintain a delicate balance. Disruptions in serotonin signaling can have implications for cardiovascular health.
For example, abnormalities in serotonin signaling have been observed in conditions such as hypertension (high blood pressure) and certain cardiovascular diseases.
Excessive vasoconstriction caused by increased serotonin levels or hypersensitivity to serotonin receptors can contribute to elevated blood pressure. Conversely, alterations in serotonin levels or receptor function may also play a role in conditions characterized by low blood pressure.
The Surprising Link Between Serotonin and Sleep
Serotonin is involved in the complex mechanisms that govern our sleep-wake cycle, also known as the circadian rhythm.
The neurotransmitter is synthesized in the brain by neurons located in the raphe nuclei, clusters of cells in the brainstem. These neurons project to various brain regions, including sleep regulation.
One of the primary ways serotonin affects sleep is through its interaction with other neurotransmitters, particularly melatonin. Serotonin is a precursor to melatonin, a hormone that helps regulate sleep.
During the daytime, serotonin levels are relatively high, and this stimulates the production of melatonin. As daylight diminishes, serotonin levels decrease, triggering the release of melatonin, which promotes sleepiness and prepares the body for rest.
Serotonin also regulates the sleep-wake cycle by influencing the activity of different brain regions. Serotonin projections to the thalamus, a brain region involved in sensory processing, help filter and modulate sensory information during wakefulness. This helps maintain focus and attention while awake.
Additionally, serotonin interacts with other neurotransmitter systems, such as norepinephrine and dopamine, to promote wakefulness and alertness. These interactions help regulate arousal levels and cognitive functions during periods of wakefulness.
The Science of Serotonin
So what is the final word on serotonin? It’s difficult to say. The research paints a complicated picture, to say the least. But that’s sometimes parred for the course when discussing complex chemical processes.
For now, it seems clear that serotonin functions in ways that are nearly as diverse as the brain itself. There is no doubt, however, that serotonin is an important part of normal brain function—we just have a lot more work to do before we understand exactly what those mechanisms are.
Naturally, it’s impossible to predict the exact amount a person should take, but as long as they get enough sleep and their diet is balanced and healthy, there shouldn’t be any need to worry about taking too much.
What Is the Function of Serotonin?
The function of serotonin is to regulate various bodily processes, including mood, appetite, digestion, and sleep.
Which Serotonin Receptors Affect Sexual Function?
Several serotonin receptors affect sexual function, including 5-HT1A, 5-HT2A, and 5-HT2C receptors.
How Does Methamphetamines Affect Serotonin Function?
Methamphetamines can affect serotonin function by increasing its release and blocking its reuptake, leading to an excessive amount of serotonin in the brain. This can cause various physical and psychological effects, including increased heart rate, high blood pressure, and anxiety.
Bakshi, A., & Tadi, P. (2022, October 5). Biochemistry, Serotonin - StatPearls - NCBI Bookshelf. Biochemistry, Serotonin - StatPearls - NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK560856/
Kanova, M., & Kohout, P. (2021, May 3). Serotonin—Its Synthesis and Roles in the Healthy and the Critically Ill. International Journal of Molecular Sciences, 22(9), 4837. https://doi.org/10.3390/ijms22094837
Berger, M., Gray, J. A., & Roth, B. L. (2009, February 1). The Expanded Biology of Serotonin. Annual Review of Medicine, 60(1), 355–366. https://doi.org/10.1146/annurev.med.60.042307.110802
Seo, D., Patrick, C. J., & Kennealy, P. J. (2008, October). Role of serotonin and dopamine system interactions in the neurobiology of impulsive aggression and its comorbidity with other clinical disorders. Aggression and Violent Behavior, 13(5), 383–395. https://doi.org/10.1016/j.avb.2008.06.003
Teleanu, R. I., Niculescu, A. G., Roza, E., Vladâcenco, O., Grumezescu, A. M., & Teleanu, D. M. (2022, May 25). Neurotransmitters—Key Factors in Neurological and Neurodegenerative Disorders of the Central Nervous System. International Journal of Molecular Sciences, 23(11), 5954. https://doi.org/10.3390/ijms23115954
Rădulescu, I., Drăgoi, A., Trifu, S., & Cristea, M. (2021, August 5). Neuroplasticity and depression: Rewiring the brain’s networks through pharmacological therapy (Review). Experimental and Therapeutic Medicine, 22(4). https://doi.org/10.3892/etm.2021.10565
- Terry, N. A., & Margolis, K. G. (2016). Serotonergic Mechanisms Regulating the GI Tract: Experimental Evidence and Therapeutic Relevance. In Handbook of experimental pharmacology (pp. 319–342). Springer Science+Business Media. https://doi.org/10.1007/164_2016_103
- Latorre, R., Sternini, C., De Giorgio, R., & Meerveld, B. G. (2015). Enteroendocrine cells: a review of their role in brain-gut communication. Neurogastroenterology and Motility, 28(5), 620–630. https://doi.org/10.1111/nmo.12754
- Camilleri, M. (2009). Serotonin in the gastrointestinal tract. Current Opinion in Endocrinology, Diabetes and Obesity, 16(1), 53–59. https://doi.org/10.1097/med.0b013e32831e9c8e
- Ormsbee, H., & Fondacaro, J. D. (1985). Action of Serotonin on the Gastrointestinal Tract. Experimental Biology and Medicine, 178(3), 333–338. https://doi.org/10.3181/00379727-178-42016
- Herath, M., Hosie, S., Bornstein, J. C., Franks, A. E., & Hill-Yardin, E. L. (2020). The Role of the Gastrointestinal Mucus System in Intestinal Homeostasis: Implications for Neurological Disorders. Frontiers in Cellular and Infection Microbiology, 10. https://doi.org/10.3389/fcimb.2020.00248
- Johansson, M. E. V., Sjövall, H., & Hansson, G. C. (2013). The gastrointestinal mucus system in health and disease. Nature Reviews Gastroenterology & Hepatology, 10(6), 352–361. https://doi.org/10.1038/nrgastro.2013.35
- Vahora, I. S., Tsouklidis, N., Kumar, R., Soni, R., & Khan, S. (2020). How Serotonin Level Fluctuation Affects the Effectiveness of Treatment in Irritable Bowel Syndrome. Cureus. https://doi.org/10.7759/cureus.9871
- Periayah, M. H., Halim, A. S., & Saad, A. Z. M. (2017). Mechanism Action of Platelets and Crucial Blood Coagulation Pathways in Hemostasis. PubMed, 11(4), 319–327. https://pubmed.ncbi.nlm.nih.gov/29340130
- Gordan, R., Gwathmey, J. K., & Xie, L. (2015). Autonomic and endocrine control of cardiovascular function. World Journal of Cardiology, 7(4), 204. https://doi.org/10.4330/wjc.v7.i4.204
- Yekehtaz, H., Farokhnia, M., & Akhondzadeh, S. (2013). Cardiovascular considerations in antidepressant therapy: an evidence-based review. DOAJ (DOAJ: Directory of Open Access Journals), 8(4), 169–176. https://doaj.org/article/07ff9a778f0b49b69554ea9fa1d6b85c
- Watts, S. W., Morrison, S. F., Davis, R. H., & Barman, S. M. (2012). Serotonin and Blood Pressure Regulation. Pharmacological Reviews, 64(2), 359–388. https://doi.org/10.1124/pr.111.004697
- Scotton, W. J., Hill, L., Williams, A. C., & Barnes, N. M. (2019). Serotonin Syndrome: Pathophysiology, Clinical Features, Management, and Potential Future Directions. International Journal of Tryptophan Research, 12, 117864691987392. https://doi.org/10.1177/1178646919873925
- Foster, R. G. (2020). Sleep, circadian rhythms and health. Interface Focus, 10(3), 20190098. https://doi.org/10.1098/rsfs.2019.0098
- Schwartz, J. D., & Roth, T. (2008). Neurophysiology of Sleep and Wakefulness: Basic Science and Clinical Implications. Current Neuropharmacology, 6(4), 367–378. https://doi.org/10.2174/157015908787386050
- Brown, R. E., Basheer, R., Mckenna, J. T., Strecker, R. E., & McCarley, R. W. (2012). Control of Sleep and Wakefulness. Physiological Reviews, 92(3), 1087–1187. https://doi.org/10.1152/physrev.00032.2011