Serotonin

Serotonin is a neurotransmitter. Its chemical name is 5-Hydroxytryptamine or 5-HT. It is derived from tryptophan. Serotonin is found in all vertebrates, mainly in the gastrointestinal tract, blood platelets and central nervous system. Its name is derived from its effect on blood pressure: serotonin is a part of the serum which regulates the tonus of blood vessels.

Serotonin does several jobs within the human body. Unlike dopamine, serotonin causes happiness, while dopamine causes pleasure.^[1] It is believed to regulate mood, intestinal activity and appetite, memory, and sleep. Many antidepressant medications are thought to work by increasing the levels of serotonin in the body^[2][3] even though depression is not caused by low serotonin. Some non-medical treatments for depression have also been shown to raise serotonin levels.^[4]

Serotonin is also found in insect venom, fungi and plants.^[5] Its presence in the seeds of many fruits helps speed those seeds through the digestive tract of animals that consume them.^[6] In insect venom, it causes pain, and sometimes death, through its effect on smooth muscle contraction.^[7]

Serotonin is involved in social rank. A lobster injected with serotonin behaves like an alpha male.^[8]