Editing Dopamine (section)

===Animals===
Dopamine is used as a neurotransmitter in most multicellular animals.<ref name=Barron/> In [[sponge]]s there is only a single report of the presence of dopamine, with no indication of its function;<ref>{{cite journal |year=2004 |title=Isolation of Araguspongine M, a new stereoisomer of an Araguspongine/Xestospongin alkaloid, and dopamine from the marine sponge ''Neopetrosia exigua'' collected in Palau |journal=Marine Drugs |volume=2 |issue=4 |pages=154–63 |vauthors=Liu H, Mishima Y, Fujiwara T, Nagai H, Kitazawa A, Mine Y, etal |doi=10.3390/md204154|pmc=3783253 |doi-access=free }}</ref> however, dopamine has been reported in the nervous systems of many other [[symmetry in biology#radially symmetric|radially symmetric]] species, including the [[cnidarian]] [[jellyfish]], [[hydra (genus)|hydra]] and some [[coral]]s.<ref>{{cite journal | vauthors = Kass-Simon G, Pierobon P | title = Cnidarian chemical neurotransmission, an updated overview | journal = Comparative Biochemistry and Physiology. Part A, Molecular & Integrative Physiology | volume = 146 | issue = 1 | pages = 9–25 | date = January 2007 | pmid = 17101286 | doi = 10.1016/j.cbpa.2006.09.008 }}</ref> This dates the emergence of dopamine as a neurotransmitter back to the earliest appearance of the nervous system, over 500 million years ago in the [[Cambrian]] Period. Dopamine functions as a neurotransmitter in [[vertebrate]]s, [[echinoderm]]s, [[arthropod]]s, [[mollusca|molluscs]], and several types of [[worm]].<ref name="Cottrell">{{cite journal | vauthors = Cottrell GA | title = Occurrence of dopamine and noradrenaline in the nervous tissue of some invertebrate species | journal = British Journal of Pharmacology and Chemotherapy | volume = 29 | issue = 1 | pages = 63–69 | date = January 1967 | pmid = 19108240 | pmc = 1557178 | doi = 10.1111/j.1476-5381.1967.tb01939.x }}</ref><ref>{{cite journal | vauthors = Kindt KS, Quast KB, Giles AC, De S, Hendrey D, Nicastro I, Rankin CH, Schafer WR | s2cid = 2092645 | title = Dopamine mediates context-dependent modulation of sensory plasticity in C. elegans | journal = Neuron | volume = 55 | issue = 4 | pages = 662–76 | date = August 2007 | pmid = 17698017 | doi = 10.1016/j.neuron.2007.07.023 | doi-access = free }}</ref>

In every type of animal that has been examined, dopamine has been seen to modify motor behavior.<ref name="Barron">{{cite journal | vauthors = Barron AB, Søvik E, Cornish JL | title = The roles of dopamine and related compounds in reward-seeking behavior across animal phyla | journal = Frontiers in Behavioral Neuroscience | volume = 4 | pages = 163 | year = 2010 | pmid = 21048897 | pmc = 2967375 | doi = 10.3389/fnbeh.2010.00163 | doi-access = free }}</ref> In the [[model organism]], [[nematode]] ''[[Caenorhabditis elegans]]'', it reduces [[animal locomotion|locomotion]] and increases food-exploratory movements; in [[flatworm]]s it produces "screw-like" movements; in [[leech]]es it inhibits swimming and promotes crawling. Across a wide range of vertebrates, dopamine has an "activating" effect on behavior-switching and response selection, comparable to its effect in mammals.<ref name=Barron/><ref>{{cite journal | vauthors = Kalivas PW, Stewart J | s2cid = 10775295 | title = Dopamine transmission in the initiation and expression of drug- and stress-induced sensitization of motor activity | journal = Brain Research. Brain Research Reviews | volume = 16 | issue = 3 | pages = 223–44 | date = 1 September 1991 | pmid = 1665095 | doi = 10.1016/0165-0173(91)90007-U }}</ref>

Dopamine has also consistently been shown to play a role in reward learning, in all animal groups.<ref name=Barron/> As in all vertebrates – [[invertebrate]]s such as [[Nematodes|roundworms]], [[flatworm]]s, [[mollusc]]s and [[Drosophila melanogaster|common fruit flies]] can all be trained to repeat an action if it is consistently followed by an increase in dopamine levels.<ref name="Barron"/> In [[Drosophila melanogaster|fruit flies]], distinct elements for reward learning suggest a modular structure to the insect reward processing system that broadly parallels that in the mammalian one.<ref>{{cite journal | vauthors = Perry CJ, Barron AB | s2cid = 19678766 | title = Neural mechanisms of reward in insects | journal = Annual Review of Entomology | volume = 58 | issue = 1 | pages = 543–62 | date = 2013 | pmid = 23020615 | doi = 10.1146/annurev-ento-120811-153631 | url = http://pdfs.semanticscholar.org/5526/26c5fe0572b4d6419555a1976877c757b0da.pdf | archive-url = https://web.archive.org/web/20200605184440/http://pdfs.semanticscholar.org/5526/26c5fe0572b4d6419555a1976877c757b0da.pdf | url-status = dead | archive-date = 2020-06-05 }}</ref> For example, dopamine regulates short- and long-term learning in monkeys;<ref>{{cite journal | vauthors = Takikawa Y, Kawagoe R, Hikosaka O | title = A possible role of midbrain dopamine neurons in short- and long-term adaptation of saccades to position-reward mapping | journal = Journal of Neurophysiology | volume = 92 | issue = 4 | pages = 2520–29 | date = October 2004 | pmid = 15163669 | doi = 10.1152/jn.00238.2004 | s2cid = 12534057 | url = http://pdfs.semanticscholar.org/b8a6/84a6d815d43db0b2491e4d3db5c664970e6e.pdf | archive-url = https://web.archive.org/web/20190302163535/http://pdfs.semanticscholar.org/b8a6/84a6d815d43db0b2491e4d3db5c664970e6e.pdf | url-status = dead | archive-date = 2019-03-02 }}</ref> in fruit flies, different groups of dopamine neurons mediate reward signals for short- and long-term memories.<ref>{{cite journal | vauthors = Yamagata N, Ichinose T, Aso Y, Plaçais PY, Friedrich AB, Sima RJ, Preat T, Rubin GM, Tanimoto H | title = Distinct dopamine neurons mediate reward signals for short- and long-term memories | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 112 | issue = 2 | pages = 578–83 | date = January 2015 | pmid = 25548178 | doi = 10.1073/pnas.1421930112 | pmc = 4299218 | bibcode = 2015PNAS..112..578Y | doi-access = free }}</ref>

It had long been believed that arthropods were an exception to this with dopamine being seen as having an adverse effect. Reward was seen to be mediated instead by [[octopamine]], a neurotransmitter closely related to [[norepinephrine]].<ref name=Waddell/> More recent studies, however, have shown that dopamine does play a part in reward learning in fruit flies. It has also been found that the rewarding effect of octopamine is due to its activating a set of dopaminergic neurons not previously accessed in the research.<ref name="Waddell">{{cite journal | vauthors = Waddell S | title = Reinforcement signalling in Drosophila; dopamine does it all after all | journal = Current Opinion in Neurobiology | volume = 23 | issue = 3 | pages = 324–329 | date = June 2013 | pmid = 23391527 | pmc = 3887340 | doi = 10.1016/j.conb.2013.01.005 }}</ref> Dopamine can also be found in [[cephalopod ink]].<ref>{{cite journal | vauthors = Lucero MT, Farrington H, Gilly WF | title = Quantification of L-Dopa and Dopamine in Squid Ink: Implications for Chemoreception | journal = The Biological Bulletin | volume = 187 | issue = 1 | pages = 55–63 | date = August 1994 | pmid = 29281314 | doi = 10.2307/1542165 }}</ref>