dopamine

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dopamine

(dōp`əmēn), one of the intermediate substances in the biosynthesis of epinephrineepinephrine
, hormone important to the body's metabolism, also known as adrenaline. Epinephrine, a catecholamine, together with norepinephrine, is secreted principally by the medulla of the adrenal gland.
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 and norepinephrine. See catecholaminecatecholamine
, 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.
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.

Dopamine

A catecholamine neurotransmitter that is synthesized by certain neurons in the brain and interacts with specific receptor sites on target neurons.

Dopamine is manufactured inside dopamine neurons in a controlled manner from the amino acid precursor l -tyrosine, which mammals obtain through the normal diet. Dopamine is then stored in vesicles within the nerve terminals, which may fuse with the cell membrane to release dopamine into the synapse.

The release of neurotransmitter is controlled by a variety of factors, including the firing rate of the dopamine nerve cell (termed impulse-dependent release) and the release- and synthesis-modulating presynaptic dopamine receptors located on the dopamine nerve terminals. Since presynaptic dopamine receptors are sensitive to the cell's own neurotransmitter, they are called dopamine autoreceptors. Once released, dopamine also acts at postsynaptic receptors to influence behavior. The actions of dopamine in the synapse are terminated primarily by the reuptake of neurotransmitter into the presynaptic terminal by means of an active dopamine transporter. Dopamine may then be either repackaged into synaptic vesicles for rerelease or degraded by the enzyme monoamine oxidase. The dopamine transporter is an important site of action of the drugs cocaine and amphetamine. See Synaptic transmission

Although it was first thought that dopamine occurred only as an intermediate product formed in the biosynthesis of two other catecholamine neurotransmitters, norepinephrine and epinephrine, dopamine is now recognized as a neurotransmitter in its own right. Several distinct dopamine neuronal systems have been identified in the brain. These include systems within the hypothalamus and the pituitary gland; systems within the midbrain that project to a variety of cortical and limbic regions and basal ganglia; the retinal system; and the olfactory system. See Brain, Epinephrine, Noradrenergic system

The midbrain dopamine neurons which project to a variety of forebrain structures are critically involved in normal behavioral attention and arousal; abnormalities in the normal functioning of these systems have been implicated in a variety of disorders. For example, Parkinson's disease involves a degeneration of the midbrain dopamine neurons. This condition is often successfully treated by providing affected individuals with l -dopa, which is readily converted to dopamine in the brain. Attention deficit disorder, which is usually first diagnosed in childhood, is thought to involve dopamine systems, because the treatment of choice, methylphenidate, binds to the dopamine transporter and alters dopamine levels in the synapse. See Parkinson's disease

Drugs used to treat the major symptoms of schizophrenia are potent dopamine receptor antagonists. It is possible that certain schizophrenias are the result of increased activity in dopamine neuronal systems, but this has not as yet been conclusively demonstrated. A similar involvement of midbrain dopamine systems has been implicated in the multiple tic disorder Tourette's syndrome, which is treated, often successfully, with dopamine receptor antagonists. See Neurobiology, Schizophrenia

Dopamine

 

3,4-dihydroxyphenethylamine, hydroxytyra-mine, C6H3(OH)2CH2(CH)2(NH2), an intermediate in the biosynthesis of catecholamines, produced by the decarboxylation of dihydroxyphenylalanine (dopa).

A number of organs and tissues (for example, the liver, lungs, and intestine) contain an abundance of dopamine. Along with epinephrine and norepinephrine, dopamine is secreted in small amounts by the adrenals, an indication that dopamine may have an independent hormonal function. Dopamine is present in the central nervous system, mainly in the motor centers, where it acts as a mediator. Healthy persons excrete an average of between 210 and 255 μg of dopamine daily with urine.

dopamine

[′dō·pə‚mēn]
(biochemistry)
C8H11O2N An intermediate in epinephrine and norepinephrine biosynthesis; the decarboxylation product of dopa.
References in periodicals archive ?
If patients have not responded to dopamine agonists or prefer to avoid this class of medications, gabapentin enacarbil is likely a good option.
Safinamide is an alpha-aminoamide that is currently being developed as an add-on therapy to dopamine agonists or to levodopa in patients with early or mid- to late-stage Parkinson's disease (PD).
Furthermore, treatment with dopamine agonist would not have been prescribed for over 2 years in an attempt to promote fertility, and an alternate cause of the symptomatology would have been investigated and appropriate treatment prescribed at an earlier time.
The development and resolution of impulse control disorders in patients with Parkinson's disease appears to be largely reliant on gender, daily dose of dopamine agonists, and the presence of depressive symptoms, according to the findings of a prospective investigation.
Mark Robson, 56, became obsessed with gambling after taking the dopamine agonist drug to control the symptoms of Parkinson's.
This clinical program is designed to investigate safinamide as an add-on therapy to dopamine agonist therapy in patients with early Parkinson's disease and as an add-on to levodopa therapy in patients with advanced Parkinson's disease.
Exposure to a dopamine agonist, or dopamine-agonist withdrawal, within the past 72 hours.
Apomorphine (Apokyn) is a dopamine agonist available in injectible form for acute "off" episodes in advanced PD.
Topics include the role pituitary tropic status has in tumor development, the estrous cycle as an instigator of anterior pituitary cell renewal, bone morphogenetic Protein-4 control of pituitary pathophysiology, and an animal model of prolactinoma, estrogen-treated animals to use in studies, the question of whether dopamine agonist treatment should be life-long, pituitary differentiation and regulation and the implications in hormone research, the regulation of growth hormone sensitivity by sex steroid, gene therapy in the neuroendocrine system, expression of somatostatin receptor subtypes and treatment outcomes, and new aspects in the diagnosis and treatment of Cushing Disease.
This tumor has a very, very high chance of responding to dopamine agonist therapy," said Dr.
To demonstrate how dopamine contributes to the physical effects of going cold turkey, Harris and Aston-Jones gave a dopamine agonist, a compound that mimics dopamine's action, to rats addicted to morphine.
Claims data analysis also indicates that patients more frequently added Azilect to a dopamine agonist than switched from a dopamine agonist to Azilect.