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<p><span id="History" class="mw-headline"><font color="#000000"><strongfont size="3">Dopamine</strong> is a catecholamine neurotransmitter present in a wide variety of animals, including both vertebrates and invertebrates. In the brain, this phenethylamine functions as a neurotransmitter, activating the five types of dopamine receptors—D<sub><font size="2">1</font></sub>D1, D<sub><font size="2">2</font></sub>D2, D<sub><font size="2">3</font></sub>D3, D<sub><font size="2">4</font></sub>D4, and D<sub><font size="2">5</font></sub>D5—and their variants. Dopamine is produced in several areas of the brain, including the substantia nigra and the ventral tegmental area.<sup id="cite_ref-0" class="reference"><font size="2"><span>[</span>1<span>]</span></font></sup> Dopamine is also a neurohormone released by the hypothalamus. Its main function as a hormone is to inhibit the release of prolactin from the anterior lobe of the pituitary.<br /font><br /p> <p><font color="#000000">Dopamine is available as an intravenous medication acting on the sympathetic nervous system, producing effects such as increased heart rate and blood pressure. However, because dopamine cannot cross the blood-brain barrier, dopamine given as a drug does not directly affect the central nervous system. To increase the amount of dopamine in the brains of patients with diseases such as Parkinson's disease and dopa-responsive dystonia, L-DOPA, which is the precursor of dopamine, can be given because it can cross the blood-brain barrier.<br /></font><br /p><h2font size="5"><span id="strong>History" class="mw-headline"</strong></font color="#000000">History</font></span></h2p>
<p><font color="#000000">Dopamine was first synthesized in 1910 by George Barger and James Ewens at Wellcome Laboratories in London, England.<sup id="cite_ref-1" class="reference"><font size="2"><span>[</span>2<span>]</span></font></sup> It was named dopamine because it was a monoamine, and its synthetic precursor was 3,4-<em>d</em>ihydr<em>o</em>xy<em>p</em>henyl<em>a</em>lanine (L-DOPA). Dopamine's function as a neurotransmitter was first recognized in 1958 by Arvid Carlsson and Nils-Åke Hillarp at the Laboratory for Chemical Pharmacology of the National Heart Institute of Sweden.<sup id="cite_ref-2" class="reference"><font size="2"><span>[</span>3<span>]</span></font></sup> Carlsson was awarded the 2000 Nobel Prize in Physiology or Medicine for showing that dopamine is not just a precursor of norepinephrine (noradrenaline) and epinephrine (adrenaline), but a neurotransmitter as well.</font></p>
<h2p><span id="Biochemistry" class="mw-headline"><font color="#000000"size="5"><strong>Biochemistry</strong></font></span></h2p>
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<div style="WIDTH: 222px" class="thumbinner"><font color="#000000"><img class="thumbimage" alt="" width="220" height="500" src="http://upload.wikimedia.org/wikipedia/commons/thumb/0/08/Catecholamines_biosynthesis.svg/220px-Catecholamines_biosynthesis.svg.png" /> </font>
<p><font color="#000000">Dopamine has the chemical formula C<sub><font size="2">6</font></sub>H<sub><font size="2">3</font></sub>(OH)<sub><font size="2">2</font></sub>-CH<sub><font size="2">2</font></sub>-CH<sub><font size="2">2</font></sub>-NH<sub><font size="2">2</font></sub>. Its chemical name is "4-(2-aminoethyl)benzene-1,2-diol" and its abbreviation is "DA."</font></p>
<p><font color="#000000">As a member of the catecholamine family, dopamine is a precursor to norepinephrine (noradrenaline) and then epinephrine (adrenaline) in the biosynthetic pathways for these neurotransmitters.</font></p>
<h3p><span id="Biosynthesis" class="mw-headline"><font color="#000000"size="5"><strong>Biosynthesis</strong></font></span></h3p>
<p><font color="#000000">Dopamine is biosynthesized in the body (mainly by nervous tissue and the medulla of the adrenal glands) first by the hydroxylation of the amino acid L-tyrosine to L-DOPA via the enzyme tyrosine 3-monooxygenase, also known as tyrosine hydroxylase, and then by the decarboxylation of L-DOPA by aromatic L-amino acid decarboxylase (which is often referred to as dopa decarboxylase). In some neurons, dopamine is further processed into norepinephrine by dopamine beta-hydroxylase.</font></p>
<p><font color="#000000">In neurons, dopamine is packaged after synthesis into vesicles, which are then released into the synapse in response to a presynaptic action potential.</font></p>
