An important neurotransmitter (messenger) in the brain. Dopamine is classified as a catecholamine (a class of molecules that serve as neurotransmitters and hormones). It is a monoamine (a compound containing nitrogen formed from ammonia by replacement of one or more of the hydrogen atoms by hydrocarbon radicals). Dopamine is a precursor (forerunner) of adrenaline and a closely related molecule, noradrenaline. Dopamine is formed by the decarboxylation (removal of a carboxyl group) from dopa. Dopa is used in the treatment of Parkinson disease. Parkinson disease is believed to be related to low levels of dopamine in certain parts of the brain. When dopa is taken by mouth, it crosses through the blood-brain barrier. Once it has crossed from the bloodstream into the brain, it is converted to dopamine. The resulting increase in dopamine concentrations in the brain is thought to improve nerve conduction and to assist in lessening the movement disorders in Parkinson disease. In 1970 the FDA (Food and Drug Administration) approved dopa in the form of L-Dopa, or levodopa, for use in the US. The drug revolutionized the treatment of Parkinson disease.
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An intermediate in tyrosine metabolism and precursor of norepinephrine and epinephrine; it accounts for 90% of the catecholamines; its presence in the central nervous system and localization in the basal ganglia (caudate and lentiform nuclei) suggest that d. may have other functions. Depletion of d. produces Parkinson disease. SYN: 3-hydroxytyramine, decarboxylated dopa.
- d. hydrochloride a biogenic amine and neural transmitter substance, used as a vasopressor agent for treatment of shock.
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do·pa·mine 'dō-pə-.mēn n a monoamine C8H11NO2 that is a decarboxylated form of dopa and occurs esp. as a neurotransmitter in the brain and as an intermediate in the biosynthesis of epinephrine see INTROPIN

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a catecholamines derived from dopa that functions as a neurotransmitter, acting on specific dopamine receptors and also on adrenergic receptors throughout the body, especially in the limbic system and extrapyramidal system of the brain and in the arteries and the heart. It also stimulates the release of noradrenaline from nerve endings. The effects vary with the concentration. Dopamine is used as a drug to increase the strength of contraction of the heart in heart failure, shock, severe trauma, and septicaemia. It is administered by injection in carefully controlled dosage. Possible side-effects include unduly rapid or irregular heartbeat, nausea, vomiting, breathlessness, angina pectoris, and kidney damage.
Certain drugs (dopamine receptor agonists) have an effect on the body similar to that of dopamine. They include apomorphine, bromocriptine, pergolide, ropinirole, and cabergoline (Cabaser) and are used to treat parkinsonism. Drugs that compete with dopamine to occupy and block the dopamine receptor sites in the body are known as dopamine receptor antagonists. They include some antipsychotic drugs (e.g. the phenothiazines and butyrophenone) and certain drugs (e.g. domperidone and metoclopramide) used to treat nausea and vomiting.

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do·pa·mine (doґpə-mēn) 3,4-dihydroxyphenylethylamine, a catecholamine formed in the body by the decarboxylation of dopa; it is an intermediate product in the synthesis of norepinephrine, and acts as a neurotransmitter in the central nervous system. It is also produced peripherally and acts on peripheral receptors, e.g., in blood vessels. Called also 3-hydroxytyramine.

Medical dictionary. 2011.

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