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| target_tissues = System-wide
| receptors = [[Dopamine receptor D1|D<sub>1</sub>]], [[Dopamine receptor D2|D<sub>2</sub>]], [[Dopamine receptor D3|D<sub>3</sub>]], [[Dopamine receptor D4|D<sub>4</sub>]], [[Dopamine receptor D5|D<sub>5</sub>]], [[TAAR1]]<ref name="DA IUPHAR"/>
| agonists = Direct: [[apomorphine]], [[bromocriptine]]<br/>[[Indirect agonist|Indirect]]: [[cocaine]], [[amphetamine]],[[methylphenidate]]
| antagonists = [[Neuroleptic]]s, [[metoclopramide]], [[domperidone]]
| precursor = [[Phenylalanine]], [[tyrosine]], and [[L-DOPA]]
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[[File:Bananas white background DS.jpg|thumb|right|Dopamine can be found in the [[Banana peel|peel]] and fruit pulp of [[bananas]].|alt=Photo of a bunch of bananas.]]
Many plants, including a variety of food plants, synthesize dopamine to varying degrees.<ref name=Kulma/> The highest concentrations have been observed in bananas—the fruit pulp of [[red banana|red]] and [[Cavendish banana|yellow bananas]] contains dopamine at levels of 40 to 50 parts per million by weight.<ref name=Kulma/> Potatoes, avocados, broccoli, and Brussels sprouts may also contain dopamine at levels of 1 part per million or more; oranges, tomatoes, spinach, beans, and other plants contain measurable concentrations less than 1 part per million.<ref name=Kulma>{{cite journal |vauthors=Kulma A, Szopa J |title=Catecholamines are active compounds in plants |journal=Plant Science |year=2007 |volume=172 |pages=433–40 |doi=10.1016/j.plantsci.2006.10.013 |issue=3|bibcode=2007PlnSc.172..433K }}</ref> The dopamine in plants is synthesized from the amino acid tyrosine, by biochemical mechanisms similar to those that animals use.<ref name=Kulma/> It can be metabolized in a variety of ways, producing [[melanin]] and a variety of [[alkaloid]]s as byproducts.<ref name=Kulma/> The functions of plant catecholamines have not been clearly established, but there is evidence that they play a role in the response to stressors such as bacterial infection, act as growth-promoting factors in some situations, and modify the way that sugars are metabolized. The receptors that mediate these actions have not yet been identified, nor have the intracellular mechanisms that they activate.<ref name=Kulma/>
Dopamine consumed in food cannot act on the brain, because it cannot cross the blood–brain barrier.<ref name="Nice-pharma"/> However, there are also a variety of plants that contain L-DOPA, the metabolic precursor of dopamine.<ref name=Ingle>{{cite journal | vauthors = Ingle PK |year=2003 |title=L-DOPA bearing plants |journal=Natural Product Radiance |volume=2 |pages=126–33 |url=http://nopr.niscair.res.in/bitstream/123456789/12261/1/NPR%202%283%29%20126-133.pdf |archive-url=https://web.archive.org/web/20140302114720/http://nopr.niscair.res.in/bitstream/123456789/12261/1/NPR%202%283%29%20126-133.pdf |archive-date=2014-03-02 |url-status=live |access-date=24 September 2015}}</ref> The highest concentrations are found in the leaves and bean pods of plants of the genus ''[[Mucuna]]'', especially in ''[[Mucuna pruriens]]'' (velvet beans), which have been used as a source for L-DOPA as a drug.<ref>{{cite journal |year=1993 |title=Occurrence of L-DOPA and dopamine in plants and cell cultures of ''Mucuna pruriens'' and effects of 2, 4-d and NaCl on these compounds |journal=Plant Cell, Tissue and Organ Culture |volume=33 |issue=3 |pages=259–64 |doi=10.1007/BF02319010 | vauthors = Wichers HJ, Visser JF, Huizing HJ, Pras N|s2cid=44814336 }}</ref> Another plant containing substantial amounts of L-DOPA is ''[[Vicia faba]]'', the plant that produces fava beans (also known as "broad beans"). The level of L-DOPA in the beans, however, is much lower than in the pod shells and other parts of the plant.<ref>{{cite journal | vauthors = Longo R, Castellani A, Sberze P, Tibolla M | title = Distribution of l-dopa and related amino acids in Vicia | journal = Phytochemistry | year = 1974 | volume = 13 | issue = 1 | pages = 167–71 | doi = 10.1016/S0031-9422(00)91287-1| bibcode = 1974PChem..13..167L }}</ref> The seeds of ''[[Cassia (genus)|Cassia]]'' and ''[[Bauhinia]]'' trees also contain substantial amounts of L-DOPA.<ref name=Ingle/>
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