dopamine


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Related to dopamine: norepinephrine, serotonin

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 ?
Effect of acute ethanol on striatal dopamine neurotransmission in ambulatory rats.
The fetal dopamine cells that will be used within TRANSEURO, however, carry some restrictions.
It gives new insights into the pharmacology of four different classes of widely used antidepressants that act on certain transporter proteins, including transporters for dopamine, serotonin and noradrenaline.
When both dopamine and glutamate were blocked, the rats did not display the extreme behaviors.
Preclinical studies indicate that while an increase in dopamine activity leads to improvements in diabetes, the time of day of the increased dopamine activity is also important.
Rice and study co-principal investigator Kenneth Carr, PhD, also conducted separate experiments with rats in which they found that animals fed low-calorie diets had a 10-fold greater sensitivity to increasing insulin levels in the brain (meaning that it took only a tenth of a rise in insulin levels as seen in rats on a normal diet to spur dopamine release).
The team found that depending on the arrangement of the dopamine D2 receptor in the brain, the mechanism of the action also changes.
Miller said that dopamine is critical to the development of methamphetamine addiction-the transition from using a drug because one likes or enjoys it to using the drug because one craves or compulsively uses it, asserting that resveratrol has been shown to regulate these dopamine neurons and to be protective in Parkinson's disease, a disorder where dopamine neurons degenerate; therefore, we sought to determine if resveratrol could affect methamphetamine-induced changes in the brain.
In the experiment, US researchers at Indiana University measured how much dopamine was released in 49 men after they had drunk 15ml of beer and a similar amount of a sports drink.
2]] Of course, there are other factors, but dopamine is the big fish in this big pond.