Information AboutSerotonin |
| CATEGORIES ABOUT SEROTONIN | |
| biogenic amines | |
| neurotransmitters | |
| tryptamines | |
| natural tryptamine alkaloids | |
Serotonin ( Pronounced ) ('''5-hydroxytryptamine''', or '''5-HT''') is a Monoamine Neurotransmitter synthesized in serotonergic Neuron s in the Central Nervous System (CNS) and Enterochromaffin Cell s in the Gastrointestinal Tract of Animals including Humans . Serotonin is also found in many Mushrooms and Plant s, including Fruit s and Vegetable s. EXPLANATION Isolated and named in and reflects the circumstances of the compound's discovery. It was initially identified as a vasoconstrictor substance in Blood Serum – hence ''serotonin'', a serum agent affecting vascular tone. This agent was later chemically identified as 5-hydroxytryptamine (5-HT) by Rapport, and, as the broad range of physiological roles were elucidated, 5-HT became the preferred name in the pharmacological field. Serotonin is synthesized extensively in the human s in the Blood stream. In the body, serotonin is synthesized from the Amino Acid Tryptophan by a short Metabolic Pathway consisting of two Enzyme s – Tryptophan Hydroxylase (TPH) and Amino Acid Decarboxylase (DDC). The TPH mediated reaction is the rate limiting step in the pathway. TPH has been shown to exist in two forms; TPH1, found in several Tissues and TPH2, which is a brain specific Isoform . There is evidence that Genetic Polymorphisms in both these subtypes influence susceptibility to anxiety and depression (Nash et al 2005; Zhang et al 2005). There is also evidence that Ovarian hormones can affect the expression of TPH in various species, suggesting a possible mechanism for Postpartum Depression and Premenstrual Stress Syndrome (Hiroi et al 2006). Serotonin taken orally does not pass into the serotonergic pathways of the central nervous system because it does not cross the Blood-brain Barrier . However, Tryptophan and its Metabolite 5-hydroxytryptophan (5-HTP), from which serotonin is synthesized, can and do cross the blood-brain barrier. These agents are available as Dietary Supplement s and may be effective serotonergic agents. One product of serotonin breakdown is 5-Hydroxyindoleacetic Acid (5 HIAA) which is excreted in the Urine . Serotonin and 5 HIAA are sometimes produced in excess amounts by certain Tumor s or Cancer s, and levels of these substances may be measured in the urine to test for these tumors. NEUROTRANSMISSION Serotonergic action is terminated primarily via Uptake of 5-HT from the synapse. This is through the specific Monoamine Transporter for 5-HT, 5-HT Reuptake Transporter , on the presynaptic neuron. Various agents can inhibit 5-HT reuptake including MDMA (ecstasy), Amphetamine , Cocaine , Dextromethorphan , Tricyclic Antidepressants (TCAs) and Selective Serotonin Reuptake Inhibitor s (SSRIs). PHARMACOLOGY The Pharmacology of 5-HT is extremely complex, with its actions being mediated by a large and diverse range of 5-HT Receptors . At least seven different receptor "families" are known to exist, each located in different parts of the body and triggering different responses. As with all neurotransmitters, the effects of 5-HT on the human mood and state of mind, and its role in consciousness, are very difficult to ascertain. RECEPTORS In the field of Neurochemistry , 5-HT Receptors are Receptors for the Neurotransmitter and Peripheral signal mediator serotonin (5-HT). 5-HT receptors are located on the cell membrane of Nerve Cells and other cell types in animals and mediate the effects of serotonin as the Endogenous Ligand and of a broad range of pharmaceutical and Hallucinogenic Drugs . With the exception of the 5-HT3 receptor, a ligand gated Ion Channel , all other 5-HT receptors are G Protein Coupled Seven Transmembrane (or ''heptahelical'') receptors that activate an Intracellular Second Messenger cascade. PSYCHEDELIC MODULATION There exist many drugs that innately modulate the 5-HT system in such a way to produce alterations in perception, emotional response, and thought process. These include . THERAPEUTIC MODULATION Various Drugs are used to modulate the 5-HT system including some Antidepressant s, Anxiolytic s, Antiemetic s, and Triptan s. MODULATING LEVELS A variety of Psychiatric Medication s affect serotonin levels, including the Monoamine Oxidase Inhibitors (MAOIs), Tricyclic Antidepressants (TCAs), Atypical Antipsychotic s, the Selective Serotonin Reuptake Inhibitor s (SSRIs), and Amphetamines . Recreational substances such as MDA , MDMA , and MDEA also affect serotonin levels. Research by GW Pharma in the UK has shown that Cannabis modulates serotonin levels through g-proteins, also resulting in an anti-nauseant effect. Antidepressants The MAOI s prevent the breakdown of monoamine neurotransmitters (including serotonin), and therefore increase concentrations of the neurotransmitter in the brain. MAOI therapy is associated with many adverse drug reactions, and patients are at risk of hypertensive crisis triggered by foods with high Tyramine -content and certain drugs. Some drugs inhibit this re-uptake of serotonin, again making it stay in the synapse longer. The Tricyclic Antidepressants inhibit the re-uptake of both serotonin and Norepinephrine . The newer Selective Serotonin Re-uptake Inhibitors ( SSRI s) have fewer (though still numerous) side effects and fewer interactions with other drugs. Antiemetics 5-HT3 Antagonist s such as Ondansetron , Granisetron and Tropisetron are important Antiemetic agents. They are particularly important in treating the Nausea and Vomiting that occur during anticancer chemotherapy using cytotoxic drugs. Another application is in treatment of post-operative nausea and vomiting. Applications to the treatment of depression and other mental and psychological conditions have also been investigated with some positive results. Serotonin syndrome Extremely high levels of serotonin can have toxic and potentially fatal effects, causing a condition known as (ecstasy) will generally cause such symptoms but only rarely lead to true Toxicity . BACTERIA, YEAST, ALGAE, PARASITES Selective serotonin re-uptake inhibitors have been found to be toxic to algae 5. The gastrointestinal parasite '' Entamoeba Histolytica '' secretes serotonin, causing a sustained secretory diarrhea in some patients 67. Patients infected with '' Entamoeba Histolytica '' were found to have highly elevated serum serotonin levels which returned to normal following resolution of the infection. 8'' Entamoeba Histolytica '' also responds to the presence of serotonin by becoming more virulent 9. PLANTS Serotonin is found in s of the Stinging Nettle (''Urtica dioica''). It should be noted serotonin does not cross the blood-brain barrier unlike its precursors 5-HTP or tryptophan. Several plants contain serotonin together with a family of related Tryptamine s that are Methyl ated at the Amino (NH2) and Hydroxy (OH) groups, are ''N''-oxides , or miss the OH group. Example are plants from the '' Anadenanthera '' genus that are used in the Hallucinogen ic Yopo snuff. ANIMALS Serotonin as a Neurotransmitter is found in all animals, including insects. Several Toad Venom s contain serotonin and related tryptamines. REFERENCES SEE ALSO
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