SerotoninSerotonin, whose chemical name is 5-hydroxytryptamine or 5-HT, is synthesized both in serotonergic neurons in the central nervous system and in enterochromaffin cells in the gastrointestinal tract. It's classified as a monoamine neurotransmitter. When it was first discovered, it was thought to be a vasoconstrictor found in blood serum, and was misnamed – sero-, from blood serum, and –tonin, from its supposed affect on vascular tone. Today, its more accurate name 5-HT is becoming preferred in technical fields, but it is still known as serotonin in the public sphere.
Serotonin is known to play an important part in several biochemical processes and disorders, including depression, migraine headaches, bipolar disorder, anxiety, appetite, and even sexuality.
Synthesis of Serotonin
Serotonin is synthesized from tryptophan, an amino acid that has been falsely associated with turkey and its purported effect on sleepiness. Serotonin taken orally does not get to the nervous system, but remains in the blood stream due to the blood-brain barrier, but tryptophan and its metabolic derivative 5-hydroxytryptophan can enter the brain, and are thus used as dietary supplements (with untested efficacy).
Certain cancer tumors also produce serotonin and a breakdown product, 5HIAA, which are excreted in urine. High levels of either substance may indicate cancer, and are often tested for by oncologists.
Serotonin's Actions as Neurotransmitter
Most neurotransmitters are released from tiny synaptic terminal buttons at the ends of nerve cells, but serotonin appears to be different. It is instead released freely from serotonergic varicosities into the general neuronal space, diffusing over a much larger area to activate the 5-HT receptors of nearby neurons. This reuptake can be disrupted by agents like MDMA, cocaine, tricyclic antidepressants (TCAs), and selective serotonin reuptake inhibitors (SSRIs).
The overall action of serotonin is very complex and not entirely understood. It's also difficult to understand its real effect on human mood, as it acts a little differently on each subject. Psychotropic drugs like MDMA may help scientists understand. MDMA is thought to flood the brain with serotonin (as well as norepinephrine and dopamine) and causes feelings of well-being, comfort, tactile sensitivity and sometimes entactogenesis, or feelings of emotional empathy. MDEA is a related drug that appears to release only serotonin and does not cause quite the same stimulant effect.
Selective serotonin reuptake inhibitors sound as if they prevent the action of serotonin, but in actuality they maintain serotonin in the synapses longer, increasing the action of existing serotonin. MAOIs prevent the breakdown of serotonin and other monoamine neurotransmitters, which also increases the amount of serotonin available. Unfortunately, MAOIs are associated with adverse drug reactions like hypertension, usually caused by interaction with certain drugs and foods with high tyramine content.
Serotonin antagonists act as antiemetics, and are excellent for treating nausea and vomiting associated with chemotherapy, among other things. They have also been investigated for use in treating depression and certain other psychological conditions.
Serotonin Level Disorders
Deficiencies or excessive intake of certain dietary minerals and vitamins can disrupt the level of serotonin, causing disruptions in the production or reuptake processes surrounding serotonin.
When serotonin levels are increased through medical intervention, a dangerous condition known as serotonin syndrome may develop, particularly during the use of several substances that act on serotonin. Serotonin syndrome may include the following symptoms.
- Cognitive – mental confusion, hypomania, agitation, headache, coma
- Autonomic – shivering, sweating, fever, hypertension, tachycardia, nausea, diarrhea
- Somatic – myoclonus/clonus (muscle twitching), hyperreflexia, tremor
Web Resources On Serotonin
Serotonin and Judgment
Table of Neurotransmitters
Book Resources On SerotoninTryptophan, Serotonin and Melatonin : Basic Aspects and Applications by Gerald Huether et al
Neuronal Serotonin by N. N. Osborne
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