Serotonin: Difference between revisions

'''Serotonin''' (also known as '''5-hydroxytryptamine''', or '''5-HT'''), is a naturally occuring chemical found in humans, animals, and plants alike. Serotonin exerts its effects through the [[monoamine]] [[neurotransmitter|neurotransmitters]] affecting the 14 known [[serotonin]] [[receptors]] (5-HT_1A,1E,1F, 5-HT_1Dα,1Dβ, 5-HT_3,4,6,7, 5-HT_2A,2B,2C, 5-HT_5A-5B)<ref> Frazer, A., & Hensler, J. G. (1999). Serotonin. Basic neurochemistry, 6, 335-346. </ref> 90%-95% of Serotonin is located in the gastrointestinal tract, in blood platelets 8% and in the central nervous system 1%-2%.<ref>Kling, A. (2013). 5-HT2A: a serotonin receptor with a possible role in joint diseases (Doctoral dissertation, Umeå Universitet).</ref>Serotonin is commonly referred to as one of many "happy hormones" amongst dopamine, oxytocin, and endorphins, these chemicals bring about feelings of happiness and wellbeing.

Approximately 95% of the human body's serotonin is produced in the intestines, where it has been credited with effects related to hormonal, autocrine, paracrine, and endocrine actions. <ref>Terry, N., & Margolis, K. G. (2016). Serotonergic mechanisms regulating the GI tract: experimental evidence and therapeutic relevance. https://dx.doi.org/10.1007%2F164_2016_103</ref>What is not absorbed elsewhere in the body is synthesized into serotonergic [[neurons]] for use by the central nervous system or CNS, here the serotonergic neurons can regulate: sleep, appetite, sexual behavior, homeostasis/temperature regulation, pain, and cognition. Serotonin also affects pathological states such as: disorders connected to mood, anxiety, psychosis and pain.<ref>Chilmonczyk, Z., Bojarski, A. J., Pilc, A., & Sylte, I. (2015). Functional selectivity and antidepressant activity of serotonin 1A receptor ligands. International journal of molecular sciences, 16(8), 18474-18506.https://doi.org/10.3390%2Fijms160818474</ref>Having either too little or too much serotonin can have many negative effects.

In the blood, it serves as a [[vasoconstriction|vasoconstrictor]], and could be attributed as the cause of vasoconstriction in most serotonergic drugs.{{citation needed}}

Many antidepressants such as: venlafaxine (Effexor), an SNRI, citalopram (Celexa), a SSRI and amitriptyline (Elavil), a TCA these antidepressants all exert there action through serotonin reuptake inhibitors. Many recreational drugs like [[cocaine]] and [[tramadol]] are also serotonin reuptake inhibitors.

Many [[antipsychotics]] such as, [[haloperidol]] or [[quetiapine]] and anti-emetics are serotonin receptor antagonists. One example is galanolactone, a chemical found in ginger, that acts as an anti-emetic via its action as a 5-HT₃ antagonist.

Extremely high levels of serotonin can cause a condition known as serotonin syndrome, which possess both toxic and potentially life threatening effects. Serotonin syndrome, also known as serotonin toxicity, is not known to occur naturally without the introduction of a pharmaceutical or supplemental agent. However, serotonin syndrome is known to develop from naturally occurring compounds such as St. John's Wort, a treatment for depression, due to its similarities to already existing antidepressants. Excess amounts of serotonin in the brain is primarily caused by the concurrent use of two or more serotonin acting drugs.<ref>Lane, R., & Baldwin, D. (1997). Selective serotonin reuptake inhibitor-induced serotonin syndrome. Journal of clinical psychopharmacology, 17(3), 208-221.https://doi.org/10.1097/00004714-199706000-00012</ref>An example that may result in serotonin syndrome would include taking two antidepressants in combination such as Escitalopram (Lexapro) with Duloxetine (Cymbalta), since both drugs act on some of the same receptors they may cause serotonin syndrome. Another example would be taking a prescription antidepressant in combination with an over the counter cough suppressant such as [[Dextromethorphan]].<ref>Monte, A. A., Chuang, R., & Bodmer, M. (2010). Dextromethorphan, chlorphenamine and serotonin toxicity: case report and systematic literature review. British journal of clinical pharmacology, 70(6), 794-798.https://dx.doi.org/10.1111%2Fj.1365-2125.2010.03747.x</ref><ref>Schwartz, A. R., Pizon, A. F., & Brooks, D. E. (2008). Dextromethorphan-induced serotonin syndrome. Clinical Toxicology, 46(8), 771-773.https://doi.org/10.1080/15563650701668625</ref>The number of possibly dangerous combinations are numerous. If you are currently taking an antidepressant or are considering taking a new substance, ensure that no dangerous interactions exist.

Symptoms can start showing within hours and can include: increased or irregular heart rate, tremors, low-grade fever to fevers at or over 41°C (105.8°F), sweating, anxiety, hyperthermia, shivering, high blood pressure, restlessness, dilation of the pupils, overactive or over responsive reflexes, agitation, confusion, death of muscle fibers, clotting of small blood vessels, increase in body acidity, delirium, renal (kidney) failure, coma and rarely death.<ref>Frank, C. (2008). Recognition and treatment of serotonin syndrome. Canadian Family Physician, 54(7), 988-992.</ref>Symptoms in minor cases may resolves within days, moderate cases may resolve within weeks, and in severe cases permanent damage or death may occur.