n.
Any of a group of amines derived from catechol that have important physiological effects as neurotransmitters and hormones and include epinephrine, norepinephrine, and dopamine.
catecholamine
Dictionary:
cat·e·cho·la·mine (kăt'ĭ-kō'lə-mēn', -kô'-)  |
| Chemistry Dictionary: catecholamine |
Any of a class of amines that possess a catechol (C6H4(OH)2) ring. Including dopamine, adrenaline, and noradrenaline, they function as neurotransmitters and/or hormones.
| Dental Dictionary: catecholamine |
n
Any one of a group of sympathomimetic compounds composed of a catechol molecule and the aliphatic portion of amine. Some catecholamines (epinephrine and norepinephrine) are produced naturally by the body and function as key neurologic chemicals.
| Britannica Concise Encyclopedia: catecholamine |
For more information on catecholamine, visit Britannica.com.
| Columbia Encyclopedia: catecholamine |
catecholamine (kăt'əkôl'əmēn), any of several compounds occurring naturally in the body that serve as hormones or as neurotransmitters in the sympathetic nervous system. The catecholamines include such compounds as epinephrine, or adrenaline, norepinephrine, and dopamine. They resemble one another chemically in having an aromatic portion (catechol) to which is attached an amine, or nitrogen-containing group. Epinephrine and norepinephrine, which are also hormones, are secreted by the adrenal medulla, and norepinephrine is also secreted by some nerve fibers. These substances prepare the body to meet emergencies such as cold, fatigue, and shock, and norepinephrine is probably a chemical transmitter at nerve synapses. Dopamine is an intermediate in the synthesis of epinephrine; in addition, a deficiency of dopamine in the brain is responsible for the symptoms of Parkinson's disease. Medical administration of the drug L-dopa, which is presumed to be converted to dopamine in the brain, relieves the symptoms. Epinephrine is used medically to stimulate heartbeat and to treat emphysema, bronchitis, and bronchial asthma and other allergic conditions, as well as in the treatment of the eye disease glaucoma.
| Veterinary Dictionary: catecholamine |
Any of a group of sympathomimetic amines (including dopamine, epinephrine and norepinephrine), the aromatic portion of whose molecule is catechol.
The catecholamines play an important role in the body's physiological response to stress. Their release at sympathetic nerve endings increases the rate and force of muscular contraction of the heart, thereby increasing cardiac output; constricts peripheral blood vessels, resulting in elevated blood pressure; elevates blood glucose levels by hepatic and skeletal muscle glycogenolysis; and promotes an increase in blood lipids by increasing the catabolism of fats.
- c.-depleting agents — cause depletion of neuronal stores of norepinephrine, thereby reducing adrenergic responses, e.g. reserpine.
| Wikipedia: Catecholamine |
Catecholamines are sympathomimetic[1] "fight-or-flight" hormones that are released by the adrenal glands in response to stress.[2] They are part of the sympathetic nervous system.
They are called catecholamines because they contain a catechol group, and are derived from the amino acid tyrosine.[3]
The most abundant catecholamines are epinephrine (adrenaline), norepinephrine (noradrenaline) and dopamine, all of which are produced from phenylalanine and tyrosine.
Catecholamines are water-soluble and are 50% bound to plasma proteins, so they circulate in the bloodstream.
Tyrosine is created from phenylalanine by hydroxylation by the enzyme phenylalanine hydroxylase. (Tyrosine is also ingested directly from dietary protein). It is then sent to catecholamine-secreting neurons. Here, many kinds of reactions convert it to L-DOPA, to dopamine, to norepinephrine, and eventually to epinephrine.[4]
Contents |
Production
Location
Catecholamines are produced mainly by the chromaffin cells of the adrenal medulla and the postganglionic fibers of the sympathetic nervous system. Dopamine, which acts as a neurotransmitter in the central nervous system, is largely produced in neuronal cell bodies in two areas of the brainstem: the substantia nigra and the ventral tegmental area.
Synthesis
Dopamine is the first catecholamine to be synthesised from steps shown. Norepinephrine and epinephrine, in turn, are derived from further modifications of dopamine. It is important to note that the enzyme dopamine hydroxylase requires copper as a cofactor (not shown) and DOPA decarboxylase requires PLP (not shown).
Catecholamine synthesis is inhibited by alpha-Methyltyrosine, by inhibiting tyrosine-3 monooxygenase.[5]
Function
Modality
Two catecholamines, norepinephrine and dopamine, act as neuromodulators in the central nervous system and as hormones in the blood circulation. The catecholamine norepinephrine is a neuromodulator of the peripheral sympathetic nervous system but is also present in the blood (mostly through "spillover" from the synapses of the sympathetic system).
High catecholamine levels in blood are associated with stress, which can be induced from psychological reactions or environmental stressors such as elevated sound levels, intense light, or low blood sugar levels.
Extremely high levels of catecholamines (also known as catecholamine toxicity) can occur in central nervous system trauma due to stimulation and/or damage of nuclei in the brainstem, in particular those nuclei affecting the sympathetic nervous system. In emergency medicine, this occurrence is widely known as catecholamine dump.
Extremely high levels of catecholamine can also be caused by neuroendocrine tumors in the adrenal medulla, a treatable condition known as pheochromocytoma.
High levels of catecholamines can also be caused by monoamine oxidase A deficiency. This is the gene responsible for degradation of these neurotransmitters and thus increases the circulation of them considerably. It occurs in the absence of pheochromocytoma, neuroendocrine tumors, and carcinoid syndrome, but it looks similar to carcinoid syndrome such as facial flushing, aggression, and ADHD.[6][7]
Effects
Catecholamines cause general physiological changes that prepare the body for physical activity (fight-or-flight response). Some typical effects are increases in heart rate, blood pressure, blood glucose levels, and a general reaction of the sympathetic nervous system. Some drugs, like tolcapone (a central COMT-inhibitor), raise the levels of all the catecholamines.
Function in plants
"They have been found in 44 plant families, but no essential metabolic function has been established for them. They are precursors of benzo[c]phenanthridine alkaloids, which are the active principal ingredients of many medicinal plant extracts. CAs have been implicated to have a possible protective role against insect predators, injuries, and nitrogen detoxification. They have been shown to promote plant tissue growth, somatic embryogenesis from in vitro cultures, and flowering. CAs inhibit indole-3-acetic acid oxidation and enhance ethylene biosynthesis. They have also been shown to enhance synergistically various effects of gibberellins."[8]
Structure
Catecholamines have the distinct structure of a benzene ring with two hydroxyl groups, an intermediate ethyl chain, and a terminal amine group.
Degradation
They have a half-life of approximately a few minutes when circulating in the blood.
Monoamine oxidase (MAO) is the main enzyme responsible for degradation of catecholamines.
Amphetamines and MAOIs bind to MAO in order to inhibit its action of breaking down catecholamines. This is primarily the reason why the effects of amphetamines have a longer lifespan than those of cocaine and other substances. Amphetamines not only cause a release of dopamine, epinephrine, and norepinephrine into the blood stream but also suppress re-absorption.
See also
References
- ^ catecholamine at Dorland's Medical Dictionary
- ^ University of California, San Diego, Health Library, catecholamines.
- ^ Purves, Dale, George J. Augustine, David Fitzpatrick, William C. Hall, Anthony-Samuel LaMantia, James O. McNamara, and Leonard E. White (2008). Neuroscience. 4th ed. Sinauer Associates. pp. 137–8. ISBN 978-0-87893-697-7.
- ^ Joh TH, Hwang O (1987). "Dopamine beta-hydroxylase: biochemistry and molecular biology". Annals of the New York Academy of Sciences 493: 342–50. doi:. PMID 3473965.
- ^ wrongdiagnosis.com - Description of Alpha-Methyltyrosine
- ^ Manor I, Tyano S, Mel E, et al. (2002). "Family-based and association studies of monoamine oxidase A and attention deficit hyperactivity disorder (ADHD): preferential transmission of the long promoter-region repeat and its association with impaired performance on a continuous performance test (TOVA)". Molecular Psychiatry 7 (6): 626–32. doi:. PMID 12140786.
- ^ Brunner HG (1996). "MAOA deficiency and abnormal behaviour: perspectives on an association". Ciba Foundation Symposium 194: 155–64; discussion 164–7. PMID 8862875.
- ^ A. I. Kuklin and B. V. Conger, "Catecholamines in plants," Journal of Plant Growth Regulation, Springer New York ISSN 0721-7595 (Print), ISSN 1435-8107 (Online), Issue Volume 14, Number 2 / June, 1995 DOI 10.1007/BF00203119, pp. 91-97.
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| Chemistry Dictionary. A Dictionary of Chemistry. Sixth Edition. Copyright © Market House Books Ltd, 2008. All rights reserved. Read more |
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Mentioned in
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- catecholaminergic
- 3-hydroxytyramine hydrobromide (organic chemistry)
- dobutamine
- reserpine
- α-methyl-para-tyrosine (organic chemistry)
- antiadrenergic
- epinephrine/epinephrine bitartrate/epinephrine HCl
