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Serotonin |
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| Serotonin is an organic compound formed from tryptophan and found in the brain, platelets, digestive tract, and pineal gland. Serotonin is active in vasoconstriction, stimulation of the smooth muscles, transmission of impulses between nerve cells, and regulation of cyclic body processes. An adult human contains about 5 to 10 mg of serotonin, 90% of which is in the intestine and the rest in blood platelets and the brain. The chemical name for serotonin is 5-hydoxytryptamine which is often abbreviated to 5-HT. Serotonin is formed by the hydroxylation and decarboxylation of tryptophan. Serotonin production involves an enzyme named tryptophan hydroxylase. Tryptophan hydroxylase adds a hydroxyl group to tryptophan's benzene ring at position 5, creating 5-hydroxytryptophan. Another enzyme, amino acid decarboxylase, removes a carboxyl group from 5-hydroxytryptophan, leaving 5-hydroxytryptamine, or serotonin. |
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Functions and health benefits of serotonin |
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| Serotonin is believed to play an important part of the biochemistry of depression, bipolar disorder and anxiety. Serotonin has many
functions in the human body including the control of appetite, sleep, memory and learning, temperature regulation, mood, behaviour, cardiovascular function, muscle contraction, endocrine regulation and depression. Serotonin acts both as a neurotransmitter (a substance that nerves use to send messages to one another) and a vasoconstrictor (a substance that causes blood vessels to narrow). Serotonin is widely implicated in the treatment of various disorders, including anxiety, depression, obsessive-compulsive disorder, schizophrenia, stroke, obesity, pain, hypertension, vascular disorders, migraine, and nausea. Serotonin is an important monoamine neurotransmitter in both the central and peripheral nervous systems of mammals. As a neurotransmitter, serotonin regulating the delivery of messages between nerve cells (neurons). Serotonin originates in neurons deep in the midline of the brainstem. Because these neurons profile diffusely throughout the brain, serotonin can affect various brain functions. Serotonin influences the functioning of the cardiovascular, renal, immune, and gastrointestinal systems. Serotonin is an inhibitory neurotransmitter which complements excitatory sympathetic systems like adrenaline and dopamine in the CNS. Serotonin is implicated in a variety of physiological tasks, including learning and memory in the central nervous system (CNS) and emesis and peristaltic reflex in the enteric nervous system (ENS). Serotonin-active drugs are used as antidepressants and anxiolytics (anti-anxiety) drugs. |
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Serotonin and depression |
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Serotonin is a psychiatric disorder characterized by sad mood, loss of pleasure, guilt, disturbed sleep and appetite. There is sufficient evidence that suggest that depression may have a neurochemical etiology based in levels of serotonin. This is referred to as the indoleamine hypothesis of depression. Low serotonin levels are believed to be the cause of many cases of mild to severe depression which can lead to symptoms such as anxiety, apathy, fear, feelings of worthlessness, insomnia and fatigue. The newest medications used to suppress depression are collectively known as selective serotonin inhibitors (SSRIs). SSRIs work by altering the function of neurons that release serotonin by blocking the reuptake of serotonin back into the cell. Therefore the level of serotonin activity is increased in any part of the nervous system that uses this neurotransmitter as a chemical signal between cells. Depression has been linked to a lack of stimulation of the recipient neuron at a synapse. To stimulate the recipient cell, SSRIs inhibit the reuptake of serotonin. As a result, the serotonin stays in the synaptic gap longer than it normally would, and has the chance to be recognized again (and again) by the receptors of the recipient cell, which can finally be stimulated that way. |
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Selective serotonin reuptake inhibitors (SSRIs) |
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| Selective serotonin reuptake inhibitors (SSRIs) are a class of antidepressants that includes drugs such as citalopram (brand name of Celexa), fluoxetine (brand name of Prozac), paroxetine (brand name of Paxil) and sertraline (brand name of Zoloft). They act within the brain to increase the amount of the neurotransmitter, serotonin, in the synaptic gap by inhibiting its reuptake. Selective serotonin reuptake inhibitors are used to treat serious, continuing depression that interferes with a person's ability to function. Like other antidepressant drugs, they help reduce the extreme sadness, hopelessness, and lack of interest in life that are typical in people with depression. The mechanism of action for the SSRIs is the blocking of the uptake pump action on the presynaptic neuron. This increases the amount of serotonin in the synaptic cleft and at the postsynaptic serotonin receptor site, resulting in greater postsynaptic serotonin stimulation. |
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Serotonin syndrome |
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Serotonin syndrome is a condition caused by an excess of serotonin in the brain. Serotonin syndrome may result from therapeutic drug use when a patient is more sensitive to the SSRI, but it may also result from intentional self-poisoning or self-medicating. The drugs which we know most frequently contribute to this condition are the combining of MAOIs with fluoxetine or other drugs that have a powerful effect upon serotonin. The tricyclic antidepressants, lithium, MAOIs, SSRIs, ECT (electric shock treatment), tryptophan, and the serotonin agonists (fenfluramine) all enhance serotonin neurotransmission and can contribute to this syndrome. The effects of serotonin syndrome may progress from headaches, dizziness and vomiting, to coma and death. Serotonin syndrome is a clinical triad of cognitive-behavioural changes, autonomic dysfunction and neuromuscular dysfunction. Serotonin syndrome is characterized by cognitive and behavioural changes, autonomic dysfunction and neuromuscular abnormalities. The syndrome often occurs within hours or days of the addition of a new medication or the increment in dosage of the serotomimetic agent which affects serotonin metabolism. |
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Modulating serotonin levels |
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| Low levels of serotonin are associated with increased carbohydrate cravings, depression, heightened sensitivity to pain, and troubled sleep patterns. 5-Hydroxytryptophan (5-HTP) may be useful for a wide range of health problems derived from a lack of brain serotonin. 5-HTP has been used as a natural replacement for prescription antidepressants. A variety of psychiatric medications affect serotonin levels, including the monoamine oxidase inhibitors (MAOIs), tricyclic antidepressants (TCAs),atypical antipsychotics, and the selective serotonin reuptake inhibitors (SSRIs). Care must be taken in any attempt to increase serotonin levels, as a dangerous condition known as serotonin syndrome may result. This is especially a concern if multiple serotonergic agents interact to increase 5-HT levels - such as can happen when St Johns Wort is taken in combination with an SSRI. The most effective way of raising the serotonin level is with vigorous exercise. Serotonin levels are raised with increased activity and the production of serotonin is increased for some days after the activity. This is the safest way of increasing the serotonin level and there are numerous benefits to be gained by regular exercise. |
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