85-457: [REDACTED] Look up da , Da , DA , or Appendix:Variations of "da" in Wiktionary, the free dictionary. Da , DA , dA , DÄ and other variants may refer to: Arts, entertainment, and media [ edit ] DA! (band) , a Chicago post-punk band of the 1980s Da (play) , a 1978 play by Hugh Leonard Da (film) ,
170-469: A catechol structure (a benzene ring with two hydroxyl side groups) with one amine group attached via an ethyl chain. As such, dopamine is the simplest possible catecholamine , a family that also includes the neurotransmitters norepinephrine and epinephrine . The presence of a benzene ring with this amine attachment makes it a substituted phenethylamine , a family that includes numerous psychoactive drugs . Like most amines , dopamine
255-462: A vasodilator and an inhibitor of norepinephrine release from postganglionic sympathetic nerves terminals (dopamine can inhibit norepinephrine release by acting on presynaptic dopamine receptors, and also on presynaptic α-1 receptors, like norepinephrine itself). These responses might be activated by dopamine released from the carotid body under conditions of low oxygen, but whether arterial dopamine receptors perform other biologically useful functions
340-552: A 1988 film based on the play Damon Amendolara , American sports talk radio host Daniel Amos , also known as D.A. and Dä, an American Christian rock band Dennis Armand Lucchesi, who recorded the song " Ready 'n' Steady " under the name "D.A." Destination America , television channel DeviantArt or DA, a website that focuses on art Dumbledore's Army , a group formed by Harry Potter in his 5th year to teach students defensive spells Jon Moxley , formerly Dean Ambrose in WWE,
425-435: A central role in causing "wanting," associated with the appetitive or approach behavioral responses to rewarding stimuli, detailed studies have shown that dopamine cannot simply be equated with hedonic "liking" or pleasure, as reflected in the consummatory behavioral response. Dopamine neurotransmission is involved in some but not all aspects of pleasure-related cognition, since pleasure centers have been identified both within
510-434: A central role in several significant medical conditions, including Parkinson's disease , attention deficit hyperactivity disorder , Tourette syndrome , schizophrenia , bipolar disorder , and addiction . Aside from dopamine itself, there are many other important drugs that act on dopamine systems in various parts of the brain or body. Some are used for medical or recreational purposes, but neurochemists have also developed
595-433: A complex second messenger system . These receptors can be divided into two families, known as D 1 -like and D 2 -like . For receptors located on neurons in the nervous system, the ultimate effect of D 1 -like activation (D 1 and D 5 ) can be excitation (via opening of sodium channels ) or inhibition (via opening of potassium channels ); the ultimate effect of D 2 -like activation (D 2 , D 3 , and D 4 )
680-422: A crucial role in aversive learning through its effects on a number of brain regions. The posterior hypothalamus has dopamine neurons that project to the spinal cord, but their function is not well established. There is some evidence that pathology in this area plays a role in restless legs syndrome, a condition in which people have difficulty sleeping due to an overwhelming compulsion to constantly move parts of
765-463: A cutting utensil also known as daa Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with the title DA . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=DA&oldid=1255145918 " Category : Disambiguation pages Hidden categories: Short description
850-454: A decision-making system. The basal ganglia can be divided into several sectors, and each is involved in controlling particular types of actions. The ventral sector of the basal ganglia (containing the ventral striatum and ventral tegmental area) operates at the highest level of the hierarchy, selecting actions at the whole-organism level. The dorsal sectors (containing the dorsal striatum and substantia nigra) operate at lower levels, selecting
935-502: A defunct Israeli political party Defence Advisory Notice , a government demand in Australia and the UK not to publish or broadcast a specified news item Democratic Alliance (South Africa) , a South African political party Democratic Awakening , East German political party Department of Agriculture (Philippines) , an executive department Deutsche Alternative ("German Alternative"),
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#17328444581591020-401: A diminished ability to experience pleasure. Many types of pleasurable experiences—such as sexual intercourse, eating, and playing video games—increase dopamine release. All addictive drugs directly or indirectly affect dopamine neurotransmission in the nucleus accumbens; these drugs increase drug "wanting", leading to compulsive drug use, when repeatedly taken in high doses, presumably through
1105-479: A large degree independent of its synthesis and functions in the brain. A substantial amount of dopamine circulates in the bloodstream, but its functions there are not entirely clear. Dopamine is found in blood plasma at levels comparable to those of epinephrine, but in humans, over 95% of the dopamine in the plasma is in the form of dopamine sulfate , a conjugate produced by the enzyme sulfotransferase 1A3/1A4 acting on free dopamine. The bulk of this dopamine sulfate
1190-474: A person or animal is in a situation where several behaviors are possible, activity in the basal ganglia determines which of them is executed, by releasing that response from inhibition while continuing to inhibit other motor systems that if activated would generate competing behaviors. Thus the basal ganglia, in this concept, are responsible for initiating behaviors, but not for determining the details of how they are carried out. In other words, they essentially form
1275-624: A rightist group District attorney , (United States) chief prosecutor for a local government area, particularly a county Dreptate şi Adevăr a defunct alliance of parties in Romania Places [ edit ] Da County , a division in Sichuan, China DA postcode area , a postcode area in England Da River or Black River, a river in China and northwestern Vietnam Dah, Ivory Coast ,
1360-503: A second phasic dopamine response in certain dopaminergic cells, but rewards that are unexpected, or greater than expected, produce a short-lasting increase in synaptic dopamine, whereas the omission of an expected reward actually causes dopamine release to drop below its background level. The "prediction error" hypothesis has drawn particular interest from computational neuroscientists, because an influential computational-learning method known as temporal difference learning makes heavy use of
1445-454: A signal that encodes prediction error. This confluence of theory and data has led to a fertile interaction between neuroscientists and computer scientists interested in machine learning . Evidence from microelectrode recordings from the brains of animals shows that dopamine neurons in the ventral tegmental area (VTA) and substantia nigra are strongly activated by a wide variety of rewarding events. These reward-responsive dopamine neurons in
1530-697: A syllable in Javanese script Da. or Dòna, the honorific Mrs. in Occitan language Da Hoss , an American racehorse Dame of St Andrew , a discontinued award within the Order of Barbados Danish language (ISO 639-1 alpha-2 code DA) Dearness allowance , cost of living allowance to government employees in Bangladesh, India, and Pakistan Desk accessory , graphical programs Direct action (military) , in special operations Disadvantage , an off-case argument used by
1615-590: A village in Montagnes District, Ivory Coast, also spelt "Da" Science and technology [ edit ] Biology and medicine [ edit ] DA (chemotherapy) , standard-dose cytarabine plus daunorubicin Deoxyanthocyanidin Domoic acid , a neurotoxin produced by phytoplankton Donor-Acceptor Dopamine , a monoamine neurotransmitter Other uses in science and technology [ edit ] Dalton (unit) (symbol Da), also called
1700-495: A wrestler Degrees and licenses [ edit ] Diploma of Anesthesiology, a degree conferred by some medical institutions such as the Royal College of Anaesthetists Doctor of Arts , an academic degree Organizations [ edit ] Da! , a Russian youth movement Debtors Anonymous Air Georgia , a Georgian airline (IATA code DA) Politics and judiciary [ edit ] Da (political party) ,
1785-439: Is homovanillic acid (HVA), which has no known biological activity. From the bloodstream, homovanillic acid is filtered out by the kidneys and then excreted in the urine. The two primary metabolic routes that convert dopamine into HVA are: In clinical research on schizophrenia, measurements of homovanillic acid in plasma have been used to estimate levels of dopamine activity in the brain. A difficulty in this approach however,
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#17328444581591870-404: Is a small midbrain area that forms a component of the basal ganglia . This has two parts—an input area called the pars reticulata and an output area called the pars compacta . The dopaminergic neurons are found mainly in the pars compacta (cell group A8) and nearby (group A9). In humans, the projection of dopaminergic neurons from the substantia nigra pars compacta to the dorsal striatum, termed
1955-402: Is an organic base . As a base , it is generally protonated in acidic environments (in an acid-base reaction ). The protonated form is highly water-soluble and relatively stable, but can become oxidized if exposed to oxygen or other oxidants . In basic environments, dopamine is not protonated. In this free base form, it is less water-soluble and also more highly reactive. Because of
2040-428: Is converted into L -DOPA by the enzyme tyrosine hydroxylase , with tetrahydrobiopterin, O 2 , and iron (Fe ) as cofactors. L -DOPA is converted into dopamine by the enzyme aromatic L -amino acid decarboxylase (also known as DOPA decarboxylase), with pyridoxal phosphate as the cofactor. Dopamine itself is used as precursor in the synthesis of the neurotransmitters norepinephrine and epinephrine. Dopamine
2125-402: Is converted into norepinephrine by the enzyme dopamine β-hydroxylase , with O 2 and L -ascorbic acid as cofactors. Norepinephrine is converted into epinephrine by the enzyme phenylethanolamine N -methyltransferase with S -adenosyl- L -methionine as the cofactor. Some of the cofactors also require their own synthesis. Deficiency in any required amino acid or cofactor can impair
2210-465: Is different from Wikidata All article disambiguation pages All disambiguation pages da">da The requested page title contains unsupported characters : ">". Return to Main Page . Dopamine Dopamine ( DA , a contraction of 3,4- d ihydr o xy p henethyl amine ) is a neuromodulatory molecule that plays several important roles in cells. It is an organic chemical of
2295-406: Is ejected into the synaptic cleft . In most cases, the release of dopamine occurs through a process called exocytosis which is caused by action potentials , but it can also be caused by the activity of an intracellular trace amine-associated receptor , TAAR1 . TAAR1 is a high-affinity receptor for dopamine, trace amines , and certain substituted amphetamines that is located along membranes in
2380-422: Is especially important in treating these in newborn infants . It is given intravenously. Since the half-life of dopamine in plasma is very short—approximately one minute in adults, two minutes in newborn infants and up to five minutes in preterm infants—it is usually given in a continuous intravenous drip rather than a single injection. Its effects, depending on dosage, include an increase in sodium excretion by
2465-609: Is evidence that this mechanism may contribute to the cell loss that occurs in Parkinson's disease and other conditions. Dopamine exerts its effects by binding to and activating cell surface receptors . In humans, dopamine has a high binding affinity at dopamine receptors and human trace amine-associated receptor 1 (hTAAR1). In mammals, five subtypes of dopamine receptors have been identified, labeled from D 1 to D 5 . All of them function as metabotropic , G protein-coupled receptors , meaning that they exert their effects via
2550-474: Is located in the cells of the nephron in the kidney, where all subtypes of dopamine receptors are present. Dopamine is also synthesized there, by tubule cells, and discharged into the tubular fluid . Its actions include increasing the blood supply to the kidneys, increasing the glomerular filtration rate , and increasing the excretion of sodium in the urine. Hence, defects in renal dopamine function can lead to reduced sodium excretion and consequently result in
2635-472: Is not known. Beyond its role in modulating blood flow, there are several peripheral systems in which dopamine circulates within a limited area and performs an exocrine or paracrine function. The peripheral systems in which dopamine plays an important role include the immune system , the kidneys and the pancreas . In the immune system dopamine acts upon receptors present on immune cells, especially lymphocytes . Dopamine can also affect immune cells in
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2720-399: Is produced in the mesenteric organs. The production of dopamine sulfate is thought to be a mechanism for detoxifying dopamine that is ingested as food or produced by the digestive process—levels in the plasma typically rise more than fifty-fold after a meal. Dopamine sulfate has no known biological functions and is excreted in urine. The relatively small quantity of unconjugated dopamine in
2805-407: Is regulated by a variety of factors, including the activity of other neurons and neurotransmitter reuptake. Inside the brain, dopamine plays important roles in executive functions , motor control , motivation , arousal , reinforcement , and reward , as well as lower-level functions including lactation , sexual gratification , and nausea . The dopaminergic cell groups and pathways make up
2890-497: Is separating the high level of plasma homovanillic acid contributed by the metabolism of norepinephrine. Although dopamine is normally broken down by an oxidoreductase enzyme, it is also susceptible to oxidation by direct reaction with oxygen, yielding quinones plus various free radicals as products. The rate of oxidation can be increased by the presence of ferric iron or other factors. Quinones and free radicals produced by autoxidation of dopamine can poison cells , and there
2975-413: Is the incentive salience model, where "wanting" or desire (less commonly, "seeking" ) corresponds to appetitive or approach behavior while "liking" or pleasure corresponds to consummatory behavior. In human drug addicts , "wanting" becomes dissociated with "liking" as the desire to use an addictive drug increases, while the pleasure obtained from consuming it decreases due to drug tolerance . Within
3060-529: Is usually inhibition of the target neuron. Consequently, it is incorrect to describe dopamine itself as either excitatory or inhibitory: its effect on a target neuron depends on which types of receptors are present on the membrane of that neuron and on the internal responses of that neuron to the second messenger cAMP . D 1 receptors are the most numerous dopamine receptors in the human nervous system; D 2 receptors are next; D 3 , D 4 , and D 5 receptors are present at significantly lower levels. Inside
3145-409: The nigrostriatal pathway , plays a significant role in the control of motor function and in learning new motor skills . These neurons are especially vulnerable to damage, and when a large number of them die, the result is a parkinsonian syndrome . The ventral tegmental area (VTA) is another midbrain area. The most prominent group of VTA dopaminergic neurons projects to the prefrontal cortex via
3230-437: The D 2 sh and presynaptic D 3 receptors), which are located on the membrane of an axon terminal (the presynaptic neuron). After the postsynaptic neuron elicits an action potential, dopamine molecules quickly become unbound from their receptors. They are then absorbed back into the presynaptic cell, via reuptake mediated either by the dopamine transporter or by the plasma membrane monoamine transporter . Once back in
3315-544: The catecholamine and phenethylamine families. Dopamine constitutes about 80% of the catecholamine content in the brain. It is an amine synthesized by removing a carboxyl group from a molecule of its precursor chemical , L-DOPA , which is synthesized in the brain and kidneys. Dopamine is also synthesized in plants and most animals. In the brain, dopamine functions as a neurotransmitter —a chemical released by neurons (nerve cells) to send signals to other nerve cells. Neurotransmitters are synthesized in specific regions of
3400-399: The medulla of the adrenal glands . The primary and minor metabolic pathways respectively are: The direct precursor of dopamine, L -DOPA , can be synthesized indirectly from the essential amino acid phenylalanine or directly from the non-essential amino acid tyrosine . These amino acids are found in nearly every protein and so are readily available in food, with tyrosine being
3485-475: The mesocortical pathway and another smaller group projects to the nucleus accumbens via the mesolimbic pathway . Together, these two pathways are collectively termed the mesocorticolimbic projection . The VTA also sends dopaminergic projections to the amygdala , cingulate gyrus , hippocampus , and olfactory bulb . Mesocorticolimbic neurons play a central role in reward and other aspects of motivation. Accumulating literature shows that dopamine also plays
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3570-440: The sensitization of incentive-salience . Drugs that increase synaptic dopamine concentrations include psychostimulants such as methamphetamine and cocaine. These produce increases in "wanting" behaviors, but do not greatly alter expressions of pleasure or change levels of satiation. However, opiate drugs such as heroin and morphine produce increases in expressions of "liking" and "wanting" behaviors. Moreover, animals in which
3655-451: The spleen , bone marrow , and circulatory system . In addition, dopamine can be synthesized and released by immune cells themselves. The main effect of dopamine on lymphocytes is to reduce their activation level. The functional significance of this system is unclear, but it affords a possible route for interactions between the nervous system and immune system, and may be relevant to some autoimmune disorders. The renal dopaminergic system
3740-525: The Negative team in a policy debate Doomsday argument , a probabilistic argument based on demographics predicting how many people will be born Duck's ass or duck's arse, a haircut; particularly popular during the 1950s Dynamic game difficulty balancing , also known as difficulty adjustment or DA, an algorithm in video games. See also [ edit ] Da Da Da (disambiguation) Dah (disambiguation) The D.A. (disambiguation) Boti ,
3825-506: The VTA and substantia nigra are crucial for reward-related cognition and serve as the central component of the reward system. The function of dopamine varies in each axonal projection from the VTA and substantia nigra; for example, the VTA– nucleus accumbens shell projection assigns incentive salience ("want") to rewarding stimuli and its associated cues , the VTA– prefrontal cortex projection updates
3910-501: The activity of cone cells in the retina while suppressing rod cells —the result is to increase sensitivity to color and contrast during bright light conditions, at the cost of reduced sensitivity when the light is dim. The largest and most important sources of dopamine in the vertebrate brain are the substantia nigra and ventral tegmental area. Both structures are components of the midbrain, closely related to each other and functionally similar in many respects. The largest component of
3995-417: The arcuate nucleus is secreted into the hypophyseal portal system of the median eminence , which supplies the pituitary gland . The prolactin cells that produce prolactin, in the absence of dopamine, secrete prolactin continuously; dopamine inhibits this secretion. The zona incerta, grouped between the arcuate and periventricular nuclei, projects to several areas of the hypothalamus, and participates in
4080-490: The basal ganglia is the striatum. The substantia nigra sends a dopaminergic projection to the dorsal striatum , while the ventral tegmental area sends a similar type of dopaminergic projection to the ventral striatum . Progress in understanding the functions of the basal ganglia has been slow. The most popular hypotheses, broadly stated, propose that the basal ganglia play a central role in action selection . The action selection theory in its simplest form proposes that when
4165-532: The bloodstream and derives from the sympathetic nervous system, or it may be synthesized locally by other types of pancreatic cells. Dopamine as a manufactured medication is sold under the trade names Intropin, Dopastat, and Revimine, among others. It is on the World Health Organization's List of Essential Medicines . It is most commonly used as a stimulant drug in the treatment of severe low blood pressure , slow heart rate , and cardiac arrest . It
4250-413: The bloodstream may be produced by the sympathetic nervous system , the digestive system, or possibly other organs. It may act on dopamine receptors in peripheral tissues, or be metabolized, or be converted to norepinephrine by the enzyme dopamine beta hydroxylase , which is released into the bloodstream by the adrenal medulla. Some dopamine receptors are located in the walls of arteries, where they act as
4335-449: The body, especially the legs. The arcuate nucleus and the periventricular nucleus of the hypothalamus have dopamine neurons that form an important projection—the tuberoinfundibular pathway which goes to the pituitary gland , where it influences the secretion of the hormone prolactin . Dopamine is the primary neuroendocrine inhibitor of the secretion of prolactin from the anterior pituitary gland. Dopamine produced by neurons in
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#17328444581594420-481: The brain, but affect many regions systemically. The brain includes several distinct dopamine pathways , one of which plays a major role in the motivational component of reward-motivated behavior . The anticipation of most types of rewards increases the level of dopamine in the brain, and many addictive drugs increase dopamine release or block its reuptake into neurons following release. Other brain dopamine pathways are involved in motor control and in controlling
4505-430: The brain, dopamine functions as a neurotransmitter and neuromodulator , and is controlled by a set of mechanisms common to all monoamine neurotransmitters . After synthesis, dopamine is transported from the cytosol into secretory vesicles, including synaptic vesicles , small and large dense core vesicles by a solute carrier —a vesicular monoamine transporter , VMAT2 . Dopamine is stored in these vesicles until it
4590-479: The brain, dopamine functions partly as a global reward signal. An initial dopamine response to a rewarding stimulus encodes information about the salience , value, and context of a reward. In the context of reward-related learning, dopamine also functions as a reward prediction error signal, that is, the degree to which the value of a reward is unexpected. According to this hypothesis proposed by Montague, Dayan, and Sejnowski, rewards that are expected do not produce
4675-493: The control of gonadotropin-releasing hormone , which is necessary to activate the development of the male and female reproductive systems , following puberty. An additional group of dopamine-secreting neurons is found in the retina of the eye. These neurons are amacrine cells , meaning that they have no axons. They release dopamine into the extracellular medium, and are specifically active during daylight hours, becoming silent at night. This retinal dopamine acts to enhance
4760-582: The cytosol, dopamine can either be broken down by a monoamine oxidase or repackaged into vesicles by VMAT2, making it available for future release. In the brain the level of extracellular dopamine is modulated by two mechanisms: phasic and tonic transmission . Phasic dopamine release, like most neurotransmitter release in the nervous system, is driven directly by action potentials in the dopamine-containing cells. Tonic dopamine transmission occurs when small amounts of dopamine are released without being preceded by presynaptic action potentials. Tonic transmission
4845-627: The degree of pleasure experienced during musical chills , as measured by changes in electrodermal activity as well as subjective ratings – found that the manipulation of dopamine neurotransmission bidirectionally regulates pleasure cognition (specifically, the hedonic impact of music ) in human subjects. This research demonstrated that increased dopamine neurotransmission acts as a sine qua non condition for pleasurable hedonic reactions to music in humans. A study published in Nature in 1998 found evidence that playing video games releases dopamine in
4930-403: The development of high blood pressure . There is strong evidence that faults in the production of dopamine or in the receptors can result in a number of pathologies including oxidative stress , edema , and either genetic or essential hypertension. Oxidative stress can itself cause hypertension. Defects in the system can also be caused by genetic factors or high blood pressure. In the pancreas
5015-453: The digestive system). The pancreatic islets make up the endocrine part of the pancreas, and synthesize and secrete hormones including insulin into the bloodstream. There is evidence that the beta cells in the islets that synthesize insulin contain dopamine receptors, and that dopamine acts to reduce the amount of insulin they release. The source of their dopamine input is not clearly established—it may come from dopamine that circulates in
5100-417: The dopamine system (i.e., nucleus accumbens shell) and outside the dopamine system (i.e., ventral pallidum and parabrachial nucleus ). For example, direct electrical stimulation of dopamine pathways, using electrodes implanted in the brain, is experienced as pleasurable, and many types of animals are willing to work to obtain it. Antipsychotic drugs reduce dopamine levels and tend to cause anhedonia ,
5185-512: The dopamine system which is neuromodulatory . Dopaminergic neurons (dopamine-producing nerve cells) are comparatively few in number—a total of around 400,000 in the human brain —and their cell bodies are confined in groups to a few relatively small brain areas. However their axons project to many other brain areas, and they exert powerful effects on their targets. These dopaminergic cell groups were first mapped in 1964 by Annica Dahlström and Kjell Fuxe, who assigned them labels starting with
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#17328444581595270-605: The effects of dopamine. Parkinson's disease , a degenerative condition causing tremor and motor impairment, is caused by a loss of dopamine-secreting neurons in an area of the midbrain called the substantia nigra . Its metabolic precursor L-DOPA can be manufactured; Levodopa , a pure form of L-DOPA, is the most widely used treatment for Parkinson's. There is evidence that schizophrenia involves altered levels of dopamine activity, and most antipsychotic drugs used to treat this are dopamine antagonists which reduce dopamine activity. Similar dopamine antagonist drugs are also some of
5355-403: The extreme, psychomotor agitation and stereotyped movements . The second important effect of dopamine is as a "teaching" signal. When an action is followed by an increase in dopamine activity, the basal ganglia circuit is altered in a way that makes the same response easier to evoke when similar situations arise in the future. This is a form of operant conditioning , in which dopamine plays
5440-413: The human striatum. This dopamine is associated with learning, behavior reinforcement, attention, and sensorimotor integration. Researchers used positron emission tomography scans and C-labelled raclopride to track dopamine levels in the brain during goal-directed motor tasks and found that dopamine release was positively correlated with task performance and was greatest in the ventral striatum . This
5525-400: The immune system, it reduces the activity of lymphocytes . With the exception of the blood vessels, dopamine in each of these peripheral systems is synthesized locally and exerts its effects near the cells that release it. Several important diseases of the nervous system are associated with dysfunctions of the dopamine system, and some of the key medications used to treat them work by altering
5610-437: The increased stability and water-solubility of the protonated form, dopamine is supplied for chemical or pharmaceutical use as dopamine hydrochloride —that is, the hydrochloride salt that is created when dopamine is combined with hydrochloric acid . In dry form, dopamine hydrochloride is a fine powder which is white to yellow in color. Dopamine is synthesized in a restricted set of cell types, mainly neurons and cells in
5695-467: The intracellular milieu of the presynaptic cell; activation of the receptor can regulate dopamine signaling by inducing dopamine reuptake inhibition and efflux as well as by inhibiting neuronal firing through a diverse set of mechanisms. Once in the synapse, dopamine binds to and activates dopamine receptors. These can be postsynaptic dopamine receptors, which are located on dendrites (the postsynaptic neuron), or presynaptic autoreceptors (e.g.,
5780-659: The kidneys, an increase in urine output, an increase in heart rate , and an increase in blood pressure . At low doses it acts through the sympathetic nervous system to increase heart muscle contraction force and heart rate, thereby increasing cardiac output and blood pressure. Higher doses also cause vasoconstriction that further increases blood pressure. Older literature also describes very low doses thought to improve kidney function without other consequences, but recent reviews have concluded that doses at such low levels are not effective and may sometimes be harmful. While some effects result from stimulation of dopamine receptors,
5865-455: The letter "A" (for "aminergic"). In their scheme, areas A1 through A7 contain the neurotransmitter norepinephrine, whereas A8 through A14 contain dopamine. The dopaminergic areas they identified are the substantia nigra (groups 8 and 9); the ventral tegmental area (group 10); the posterior hypothalamus (group 11); the arcuate nucleus (group 12); the zona incerta (group 13) and the periventricular nucleus (group 14). The substantia nigra
5950-442: The most common. Although dopamine is also found in many types of food, it is incapable of crossing the blood–brain barrier that surrounds and protects the brain. It must therefore be synthesized inside the brain to perform its neuronal activity . L -Phenylalanine is converted into L -tyrosine by the enzyme phenylalanine hydroxylase , with molecular oxygen (O 2 ) and tetrahydrobiopterin as cofactors . L -Tyrosine
6035-553: The most effective anti-nausea agents . Restless legs syndrome and attention deficit hyperactivity disorder (ADHD) are associated with decreased dopamine activity. Dopaminergic stimulants can be addictive in high doses, but some are used at lower doses to treat ADHD. Dopamine itself is available as a manufactured medication for intravenous injection . It is useful in the treatment of severe heart failure or cardiogenic shock . In newborn babies it may be used for hypotension and septic shock . A dopamine molecule consists of
6120-471: The organism's behavior toward or away from achieving that outcome. Outside the central nervous system, dopamine functions primarily as a local paracrine messenger. In blood vessels, it inhibits norepinephrine release and acts as a vasodilator ; in the kidneys, it increases sodium excretion and urine output; in the pancreas, it reduces insulin production; in the digestive system, it reduces gastrointestinal motility and protects intestinal mucosa ; and in
6205-582: The prominent cardiovascular effects result from dopamine acting at α 1 , β 1 , and β 2 adrenergic receptors . Side effects of dopamine include negative effects on kidney function and irregular heartbeats . The LD 50 , or lethal dose which is expected to prove fatal in 50% of the population, has been found to be: 59 mg/kg (mouse; administered intravenously ); 95 mg/kg (mouse; administered intraperitoneally ); 163 mg/kg (rat; administered intraperitoneally); 79 mg/kg (dog; administered intravenously). The dopamine system plays
6290-405: The reasons individuals play video games vary and may include coping , socialization , and personal satisfaction. The DSM-5 defines Internet Gaming Disorder as a mental disorder closely related to Gambling Disorder. This has been supported by some researchers but has also caused controversy. Dopamine does not cross the blood–brain barrier, so its synthesis and functions in peripheral areas are to
6375-463: The release of various hormones. These pathways and cell groups form a dopamine system which is neuromodulatory . In popular culture and media, dopamine is often portrayed as the main chemical of pleasure, but the current opinion in pharmacology is that dopamine instead confers motivational salience ; in other words, dopamine signals the perceived motivational prominence (i.e., the desirability or aversiveness) of an outcome, which in turn propels
6460-444: The role of a reward signal. In the language used to discuss the reward system, reward is the attractive and motivational property of a stimulus that induces appetitive behavior (also known as approach behavior) and consummatory behavior . A rewarding stimulus is one that can induce the organism to approach it and choose to consume it. Pleasure , learning (e.g., classical and operant conditioning ), and approach behavior are
6545-508: The role of dopamine is somewhat complex. The pancreas consists of two parts, an exocrine and an endocrine component. The exocrine part synthesizes and secretes digestive enzymes and other substances, including dopamine, into the small intestine. The function of this secreted dopamine after it enters the small intestine is not clearly established—the possibilities include protecting the intestinal mucosa from damage and reducing gastrointestinal motility (the rate at which content moves through
6630-551: The specific muscles and movements that are used to implement a given behavior pattern. Dopamine contributes to the action selection process in at least two important ways. First, it sets the "threshold" for initiating actions. The higher the level of dopamine activity, the lower the impetus required to evoke a given behavior. As a consequence, high levels of dopamine lead to high levels of motor activity and impulsive behavior ; low levels of dopamine lead to torpor and slowed reactions. Parkinson's disease, in which dopamine levels in
6715-433: The substantia nigra circuit are greatly reduced, is characterized by stiffness and difficulty initiating movement—however, when people with the disease are confronted with strong stimuli such as a serious threat, their reactions can be as vigorous as those of a healthy person. In the opposite direction, drugs that increase dopamine release, such as cocaine or amphetamine, can produce heightened levels of activity, including, at
6800-414: The synthesis of dopamine, norepinephrine, and epinephrine. Dopamine is broken down into inactive metabolites by a set of enzymes— monoamine oxidase (MAO), catechol- O -methyl transferase (COMT), and aldehyde dehydrogenase (ALDH), acting in sequence. Both isoforms of monoamine oxidase, MAO-A and MAO-B , effectively metabolize dopamine. Different breakdown pathways exist but the main end-product
6885-557: The three main functions of reward. As an aspect of reward, pleasure provides a definition of reward; however, while all pleasurable stimuli are rewarding, not all rewarding stimuli are pleasurable (e.g., extrinsic rewards like money). The motivational or desirable aspect of rewarding stimuli is reflected by the approach behavior that they induce, whereas the pleasure from intrinsic rewards results from consuming them after acquiring them. A neuropsychological model which distinguishes these two components of an intrinsically rewarding stimulus
6970-741: The unified atomic mass unit Deca- or da-, an SI prefix for a factor of 10 Distribution amplifier , a device that accepts a single input signal and provides this same signal to multiple isolated outputs Double-action , a firearm operation mechanism in which the trigger both cocks and releases the hammer NZR DA class , a New Zealand diesel locomotive SJ Da , a Swedish electric locomotive Domain authority Domain Authority Sports [ edit ] U.S. Soccer Development Academy , former United States soccer league Other uses [ edit ] D.A. Wallach (born 1985), American musician and business executive Da (Javanese) ,
7055-550: The value of different goals in accordance with their incentive salience, the VTA–amygdala and VTA–hippocampus projections mediate the consolidation of reward-related memories, and both the VTA– nucleus accumbens core and substantia nigra–dorsal striatum pathways are involved in learning motor responses that facilitate the acquisition of rewarding stimuli. Some activity within the VTA dopaminergic projections appears to be associated with reward prediction as well. While dopamine has
7140-432: The ventral tegmental dopamine system has been rendered inactive do not seek food, and will starve to death if left to themselves, but if food is placed in their mouths they will consume it and show expressions indicative of pleasure. A clinical study from January 2019 that assessed the effect of a dopamine precursor ( levodopa ), dopamine antagonist ( risperidone ), and a placebo on reward responses to music – including
7225-463: Was the first study to demonstrate the behavioral conditions under which dopamine is released in humans. It highlights the ability of positron emission tomography to detect neurotransmitter fluxes during changes in behavior. According to research, potentially problematic video game use is related to personality traits such as low self-esteem and low self-efficacy, anxiety, aggression, and clinical symptoms of depression and anxiety disorders. Additionally,
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