Dopamine
IUPAC name	4-(2-aminoethyl)benzene-1,2-diol
Other names	2-(3,4-dihydroxyphenyl)ethylamine; 3,4-dihydroxyphenethylamine; 3-hydroxytyramine; DA; Intropin Revivan; Oxytyramine
Identifiers
CAS number	[51-61-6]
PubChem	681
SMILES	C1=CC(=C(C=C1CCN)O)O
Properties
Molecular formula	C8H11NO2
Molar mass	153. IUPAC Nomenclature is a system of naming Chemical compounds and of describing the science of Chemistry in general CAS registry numbers are unique numerical identifiers for Chemical compounds Polymers biological sequences mixtures and Alloys They are also referred to PubChem is a Database of chemical Molecules The system is maintained by the National Center for Biotechnology Information (NCBI a component A chemical formula is a way of expressing information about the Atoms that constitute a particular Chemical compound, and how the relationship between those atoms changes Molar mass, symbol M, is the Mass of one mole of a substance ( Chemical element or Chemical compound) 178
Melting point	128 °C (401 K)
Solubility in water	60. The melting point of a solid is the temperature range at which it changes state from solid to Liquid. Solubility is the characteristic Physical property referring to the ability of a given substance the Solute, to dissolve in a Solvent. Water is a common Chemical substance that is essential for the survival of all known forms of Life. 0 g/100 ml (? °C), solid
Hazards
R/S statement	R: 36/37/38 S: 26-36
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Dopamine is a hormone and neurotransmitter that causes happiness occurring in a wide variety of animals, including both vertebrates and invertebrates. Risk and Safety Statements, also known as R/S statements, R/S numbers, R/S phrases, and R/S sentences, is a system of Hazard codes R-phrases (short for Risk Phrases) are defined in Annex III of European Union Directive 67/548/EEC: Nature of special risks attributed to dangerous S-phrases are defined in Annex IV of European Union Directive 67/548/EEC: Safety advice concerning dangerous substances and preparations. In Chemistry, the standard state of a material is its state at 1 bar (100 Kilopascals exactly Hormones (from Greek ὁρμή - "impetus" are chemicals released by cells that affect cells in other parts of the body See Chemical synapse for an introduction to concepts and terminology used in this article In the brain, this phenethylamine functions as a neurotransmitter, activating the five types of dopamine receptors — D1, D2, D3, D4 and D5, and their variants. The human brain controls the Central nervous system (CNS by way of the Cranial nerves and Spinal cord, the Peripheral nervous system (PNS Phenethylamine, or β -phenylethylamine or 2-phenylethylamine is an Alkaloid and Monoamine. See Chemical synapse for an introduction to concepts and terminology used in this article Dopamine receptors are a class of metabotropic G protein-coupled receptors that are prominent in the Vertebrate Central nervous system (CNS Dopamine is produced in several areas of the brain, including the substantia nigra. The substantia nigra ( Latin for "black substance" Sömmering) or locus niger is a heterogeneous portion of the midbrain, separating Dopamine is also a neurohormone released by the hypothalamus. A neurohormone is any Hormone produced by neurosecretory cells usually in the Brain. The hypothalamus links the Nervous system to the Endocrine system via the Pituitary gland (hypophysis Its main function as a hormone is to inhibit the release of prolactin from the anterior lobe of the pituitary. Prolactin ( PRL) or Luteotropic hormone ( LTH) is a Peptide hormone primarily associated with Lactation. The pituitary gland, or hypophysis, is an Endocrine gland about the size of a Pea.

Dopamine can be supplied as a medication that acts on the sympathetic nervous system, producing effects such as increased heart rate and blood pressure. Medication, also referred to as medicine, can be loosely defined as any substance intended for use in the diagnosis cure mitigation treatment or prevention of disease The Sympathetic Nervous System ( SNS) is a branch of the Autonomic nervous system along with the Enteric nervous system and Parasympathetic nervous The nervous system is a Network of specialized cells that communicate information about an animal's surroundings and itself The heart is a muscular organ in all Vertebrates responsible for pumping Blood through the Blood vessels by repeated rhythmic Blood pressure is also the title of a short story by Damon Runyan in Guys and Dolls and Other Stories However, because dopamine cannot cross the blood-brain barrier, dopamine given as a drug does not directly affect the central nervous system. The blood-brain barrier (BBB is a metabolic or cellular structure in the Central nervous system (CNS that restricts the passage of various chemical substances and microscopic In Vertebrates the central nervous system ( CNS) is the part of the Nervous system which is enclosed in the Meninges. To increase the amount of dopamine in the brains of patients with diseases such as Parkinson's disease and dopa-responsive dystonia, L-DOPA (levodopa), which is the precursor of dopamine, can be given because it can cross the blood-brain barrier. Parkinson's disease (also known as Parkinson disease or PD) is a degenerative disorder of the Central nervous system that often impairs the sufferer's Dystonia is a neurological Movement disorder in which sustained muscle contractions cause twisting and repetitive movements or abnormal postures The blood-brain barrier (BBB is a metabolic or cellular structure in the Central nervous system (CNS that restricts the passage of various chemical substances and microscopic

Contents 1 History 2 Biochemistry 2.1 Name and family 2.2 Biosynthesis 2.3 Inactivation and degradation 3 Functions in the brain 3.1 Anatomy 3.2 Movement 3.3 Cognition and frontal cortex 3.4 Regulating prolactin secretion 3.5 Motivation and pleasure 3.5.1 Reinforcement 3.5.2 Reuptake inhibition, expulsion 3.5.3 Incentive salience 3.5.4 Dopamine, learning, and reward-seeking behavior 3.5.5 Animal studies 3.5.6 The effects of drugs that reduce dopamine levels in humans 3.5.7 Opioid and cannabinoid transmission 3.5.8 Sociability 3.5.9 Processing of pain 3.5.10 Salience 3.5.11 Behavior disorders 3.6 Latent inhibition and creative drive 4 Links to psychosis 5 Therapeutic use 6 Dopamine and fruit browning 7 References 8 See also 9 External links

History

Dopamine was discovered in 1952 by Arvid Carlsson and Nils-Åke Hillarp at the Laboratory for Chemical Pharmacology of the National Heart Institute of Sweden. Arvid Carlsson (born January 25, 1923) is a Swedish Scientist who is best known for his work with the Neurotransmitter Dopamine It was named dopamine because it was a monoamine, and its synthetic precursor was 3,4-dihydroxyphenylalanine (L-DOPA). Monoamine neurotransmitters are Neurotransmitters and Neuromodulators that contain one Amino group that is connected to an aromatic ring by a ^[1] Arvid 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. Arvid Carlsson (born January 25, 1923) is a Swedish Scientist who is best known for his work with the Neurotransmitter Dopamine 2000 ( MM) was a Leap year that started on Saturday of the Common Era, in accordance with the Gregorian calendar. The Nobel Prize in Physiology or Medicine (Nobelpriset i fysiologi eller medicin is awarded once a year by the Swedish Karolinska Institute. Norepinephrine ( INN) (abbreviated norepi or NE) or noradrenaline ( BAN) (abbreviated NA or NAd) is a

Dopamine was first synthesized artificially in 1910 by George Barger and James Ewens at Wellcome Laboratories in London, England. ^[2]

Biochemistry

Name and family

Dopamine has the chemical formula C₆H₃(OH)₂-CH₂-CH₂-NH₂. Its chemical name is "4-(2-aminoethyl)benzene-1,2-diol" and its abbreviation is "DA. "

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. Norepinephrine ( INN) (abbreviated norepi or NE) or noradrenaline ( BAN) (abbreviated NA or NAd) is a

Biosynthesis

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). The adrenal medulla is part of the Adrenal gland. It is located at the center of the gland being surrounded by the Adrenal cortex. In Mammals the adrenal glands (also known as suprarenal glands) are the triangle-shaped Endocrine glands that sit on top of the Kidneys their Tyrosine (abbreviated as Tyr or Y) or 4-hydroxyphenylalanine, is one of the 20 Amino acids that are used by cells to synthesize Tyrosine hydroxylase or tyrosine 3-monooxygenase is the Enzyme responsible for catalyzing the conversion of the Amino acid L-tyrosine to Decarboxylation is any Chemical reaction in which a Carboxyl group (-COOH is split off from a compound as Carbon dioxide (CO2 Aromatic L-amino acid decarboxylase ( synonyms DOPA decarboxylase Tryptophan Decarboxylase, 5-hydroxytryptophan decarboxylase AAAD is a Lyase In some neurons, dopamine is further processed into norepinephrine by dopamine beta-hydroxylase. Norepinephrine ( INN) (abbreviated norepi or NE) or noradrenaline ( BAN) (abbreviated NA or NAd) is a Dopamine β-hydroxylase (DBH is an Enzyme that converts Dopamine to Norepinephrine:Synonyms Aromatic L-amino acid decarboxylase ( Tryptophan

In neurons, dopamine is packaged after synthesis into vesicles, which are then released into the synapse in response to a presynaptic action potential. Neurons (ˈnjuːɹɒn also known as neurones and nerve cells) are responsive cells in the Nervous system that process and transmit information A vesicle is a small bubble of liquid within a cell A more formal definition in Cell biology, would be that a vesicle is a relatively small intracellular membrane-enclosed Chemical synapses are specialized junctions through which Neurons signal to each other and to non-neuronal cells such as those in Muscles or Glands In Neurophysiology, the action potential is a self-regenerating Wave of Electrochemical activity that allows Nerve cells to carry a signal

Inactivation and degradation

Dopamine is inactivated by reuptake via the dopamine transporter, then enzymatic breakdown by catechol-O-methyl transferase (COMT) and monoamine oxidase (MAO). The Dopamine transporter (also dopamine active transporter DAT SLC6A3 is a membrane-spanning protein that binds the Neurotransmitter Dopamine Catechol- O -methyl transferase ( COMT;) is one of several Enzymes that degrade Catecholamines such as Dopamine, Epinephrine Dopamine that is not broken down by enzymes is repackaged into vesicles for reuse.

Dopamine may also simply diffuse away from the synapse, and help to regulate blood pressure. Chemical synapses are specialized junctions through which Neurons signal to each other and to non-neuronal cells such as those in Muscles or Glands

Functions in the brain

Dopamine has many functions in the brain, including important roles in behavior and cognition, motor activity, motivation and reward, inhibition of prolactin production (involved in lactation), sleep, mood, attention, and learning. Cognition is a concept used in different ways by different disciplines but is generally accepted to mean the process of awareness or thought Motivation is the reason or reasons for engaging in a particular behavior especially Human behavior as studied in Philosophy, Conflict, Economics In neuroscience the reward system is a collection of brain structures which attempts to regulate and control behavior by inducing pleasurable effects Prolactin ( PRL) or Luteotropic hormone ( LTH) is a Peptide hormone primarily associated with Lactation. Lactation describes the secretion of Milk from the Mammary glands the process of providing that milk to the young and the period of time that a Mother Sleep is a Natural state of bodily rest observed throughout the animal kingdom A mood is a relatively long lasting affective or emotional state Attention is the Cognitive process of selectively concentrating on one aspect of the environment while ignoring other things In the fields of Neuropsychology, Personal development and Education, Learning is one of the most important Mental function of humans Dopaminergic neurons (i. e. , neurons whose primary neurotransmitter is dopamine) are present chiefly in the ventral tegmental area (VTA) of the midbrain, substantia nigra pars compacta, and arcuate nucleus of the hypothalamus. The ventral tegmentum or the ventral tegmental area (VTA ( tegmentum, Latin for covering) is part of the Midbrain, lying close to the Substantia In biological anatomy the mesencephalon (or midbrain) comprises the Tectum (or corpora quadrigemini Tegmentum, the ventricular mesocoelia (or "iter" The substantia nigra ( Latin for "black substance" Sömmering) or locus niger is a heterogeneous portion of the midbrain, separating The arcuate nucleus (or infundibular nucleus is an aggregation of Neurons in the mediobasal Hypothalamus, adjacent to the Third ventricle and the Median

The phasic responses of dopamine neurons are observed when an unexpected reward is presented. These responses transfer to the onset of a conditioned stimulus after repeated pairings with the reward. Classical Conditioning (also Pavlovian or Respondent Conditioning) is a form of Associative learning that was first demonstrated by Ivan Pavlov Further, dopamine neurons are depressed when the expected reward is omitted. Thus, dopamine neurons seem to encode the prediction error of rewarding outcomes. In nature, we learn to repeat behaviors that lead to maximize rewards. Dopamine is therefore believed to provide a teaching signal to parts of the brain responsible for acquiring new behavior. Temporal difference learning provides a computational model describing how the prediction error of dopamine neurons is used as a teaching signal. Temporal difference learning is a prediction method It has been mostly used for solving the Reinforcement learning problem

In insects, a similar reward system exists, using octopamine, a chemical relative of dopamine. Octopamine is a Biogenic amine which is closely related to Noradrenaline, and has Noradrenergic and Dopaminergic effects Quantitative structure-activity relationship (QSAR is the process by which Chemical structure is quantitatively correlated with a well defined process such as ^[3]

Anatomy

Main article: dopamine pathways

Dopaminergic neurons form a neurotransmitter system which originates in substantia nigra pars compacta, ventral tegmental area (VTA), and hypothalamus. Dopaminergic means "related to the Neurotransmitter Dopamine " In neuroscience neuromodulation is the process in which several classes of Neurotransmitters in the nervous system regulate diverse populations of Neurons (one The substantia nigra ( Latin for "black substance" Sömmering) or locus niger is a heterogeneous portion of the midbrain, separating The ventral tegmentum or the ventral tegmental area (VTA ( tegmentum, Latin for covering) is part of the Midbrain, lying close to the Substantia The hypothalamus links the Nervous system to the Endocrine system via the Pituitary gland (hypophysis These project axons to large areas of the brain through four major pathways:

• Mesocortical pathway
• Mesolimbic pathway
• Nigrostriatal pathway
• Tuberoinfundibular pathway

This innervation explains many of the effects of activating this dopamine system. An axon or nerve fiber is a long slender projectionof a nerve cell or Neuron, that conducts electrical impulses away from the neuron's Cell The mesocortical pathway is a Neural pathway that connects the Ventral tegmentum to the Cerebral cortex, particularly the Frontal lobes It is The mesolimbic pathway is one of the Neural pathways in the Brain that links the Ventral tegmentum in the Midbrain to the Nucleus accumbens The nigrostriatal pathway is a Neural pathway that connects the Substantia nigra with the Striatum. The tuberoinfundibular pathway refers to a population of dopamine neurons in the Arcuate nucleus of the mediobasal Hypothalamus (the 'tuberal region' that project For instance, the mesolimbic pathway connects the VTA and nucleus accumbens, both are central to the brain reward system. The mesolimbic pathway is one of the Neural pathways in the Brain that links the Ventral tegmentum in the Midbrain to the Nucleus accumbens The nucleus accumbens (NAcc also known as the accumbens nucleus or as the nucleus accumbens septi (Latin for nucleus leaning against the Septum In neuroscience the reward system is a collection of brain structures which attempts to regulate and control behavior by inducing pleasurable effects ^[4]

Movement

Via the dopamine receptors D1, D2, D3, D4 and D5, dopamine reduces the influence of the indirect pathway, and increases the actions of the direct pathway within the basal ganglia. Dopamine receptors are a class of metabotropic G protein-coupled receptors that are prominent in the Vertebrate Central nervous system (CNS The basal ganglia (or basal nuclei) are a group of nuclei in the Brain interconnected with the Cerebral cortex, Thalamus and Insufficient dopamine biosynthesis in the dopaminergic neurons can cause Parkinson's disease, in which a person loses the ability to execute smooth, controlled movements. Biosynthesis is a phenomenon wherein Chemical compounds are produced from simpler Reagents Biosynthesis unlike Chemosynthesis, takes place within living Parkinson's disease (also known as Parkinson disease or PD) is a degenerative disorder of the Central nervous system that often impairs the sufferer's The phasic dopaminergic activation seems to be crucial with respect to a lasting internal encoding of motor skills (Beck, 2005).

Cognition and frontal cortex

In the frontal lobes, dopamine controls the flow of information from other areas of the brain. The frontal lobe is an area in the Brain of Mammals It is located at the front of each Cerebral hemisphere and positioned anterior to (in front of the Dopamine disorders in this region of the brain can cause a decline in neurocognitive functions, especially memory, attention, and problem-solving. Neurocognitive is a term used to describe Cognitive functions closely linked to the function of particular areas Neural pathways or cortical networks in In Psychology, memory is an organism's ability to store retain and subsequently retrieve information Attention is the Cognitive process of selectively concentrating on one aspect of the environment while ignoring other things Problem solving forms part of thinking. Considered the most complex of all intellectual functions problem solving has been defined as higher-order Cognitive Reduced dopamine concentrations in the prefrontal cortex are thought to contribute to attention deficit disorder. ADHD predominantly inattentive (ADHD-I is one of the three subtypes of Attention-deficit hyperactivity disorder (ADHD It has been found that D1 receptors are responsible for the cognitive-enhancing effects of dopamine. ^[5] On the converse, however, anti-psychotic medications act as dopamine antagonists and are used in the treatment of positive symptoms in schizophrenia. Antipsychotics are a group of Psychoactive drugs commonly but not exclusively used to treat Psychosis, which is typified by Schizophrenia. Medication, also referred to as medicine, can be loosely defined as any substance intended for use in the diagnosis cure mitigation treatment or prevention of disease Schizophrenia ( from the Greek roots schizein (σχίζειν "to split" and phrēn

Regulating prolactin secretion

Dopamine is the primary neuroendocrine inhibitor of the secretion of prolactin from the anterior pituitary gland. Neuroendocrine nʊəroʊˈɛndəkrɪn cells are cells that release a hormone into the circulating blood in response to a neural stimulus Prolactin ( PRL) or Luteotropic hormone ( LTH) is a Peptide hormone primarily associated with Lactation. The anterior pituitary (also called the adenohypophysis, from Greek adeno, "gland" hypo, "under" physis, "growth" ^[6] Dopamine produced by neurons in the arcuate nucleus of the hypothalamus is secreted into the hypothalamo-hypophysial blood vessels of the median eminence, which supply the pituitary gland. The arcuate nucleus (or infundibular nucleus is an aggregation of Neurons in the mediobasal Hypothalamus, adjacent to the Third ventricle and the Median The median eminence is part of the inferior boundary for the Hypothalamus part of the human Brain. The pituitary gland, or hypophysis, is an Endocrine gland about the size of a Pea. The lactotrope cells that produce prolactin, in the absence of dopamine, secrete prolactin continuously; dopamine inhibits this secretion. Prolactin ( PRL) or Luteotropic hormone ( LTH) is a Peptide hormone primarily associated with Lactation. Thus, in the context of regulating prolactin secretion, dopamine is occasionally called prolactin-inhibiting factor (PIF), prolactin-inhibiting hormone (PIH), or prolactostatin. Prolactin also seems to inhibit dopamine release, such as after orgasm, and is chiefly responsible for the refractory period. An orgasm (sexual climax is the conclusion of the plateau phase of the sexual response cycle, and may be experienced by both males and females In sexuality the refractory period is the recovery phase after Orgasm during which it is physiologically impossible for an individual to have additional orgasms

Motivation and pleasure

Main article: motivation

Reinforcement

Dopamine is commonly associated with the pleasure system of the brain, providing feelings of enjoyment and reinforcement to motivate a person proactively to perform certain activities. Motivation is the reason or reasons for engaging in a particular behavior especially Human behavior as studied in Philosophy, Conflict, Economics In Operant conditioning, reinforcement is an immediate increase in the strength of a response following a change in environment Dopamine is released (particularly in areas such as the nucleus accumbens and ventral tegmental area) by naturally rewarding experiences such as food, sex,^[7][8] some drugs, and neutral stimuli that become associated with them. The nucleus accumbens (NAcc also known as the accumbens nucleus or as the nucleus accumbens septi (Latin for nucleus leaning against the Septum The ventral tegmentum or the ventral tegmental area (VTA ( tegmentum, Latin for covering) is part of the Midbrain, lying close to the Substantia Food is any substance usually composed primarily of Carbohydrates Fats water and/or Proteins that can be eaten or drunk by an Human sexual behavior or different human sexual practices encompass a wide range of activities such as strategies to find or attract partners ( Mating and display Neutral stimulus is a stimulus which initially produces no specific response other than focusing Attention. Classical Conditioning (also Pavlovian or Respondent Conditioning) is a form of Associative learning that was first demonstrated by Ivan Pavlov This theory is often discussed in terms of drugs such as cocaine, nicotine, and amphetamines, which seem to directly or indirectly lead to an increase of dopamine in these areas, and in relation to neurobiological theories of chemical addiction, arguing that these dopamine pathways are pathologically altered in addicted persons. Cocaine ( benzoylmethyl ecgonine) is a Crystalline Tropane Alkaloid that is obtained from the leaves of the Coca plant Nicotine is an Alkaloid found in the Nightshade family of plants ( Solanaceae) which constitutes approximately 0 Amphetamine, and related drugs such as Methamphetamine are a group of drugs that act by increasing levels of Norepinephrine, Serotonin, and Dopamine Neurobiology is the study of cells of the Nervous system and the organization of these cells into functional circuits that process information and mediate behavior The term " addiction " is used in many contexts to describe an obsession compulsion or excessive Physical dependence or psychological dependence such as Recent studies indicate that aggression may also stimulate the release of dopamine in this way. In Psychology and other social and Behavioral sciences aggression refers to behavior that is intended to cause harm

Reuptake inhibition, expulsion

Cocaine and amphetamines inhibit the re-uptake of dopamine; however, they both influence separate mechanisms of action. Reuptake, or re-uptake, is the reabsorption of a Neurotransmitter by the Neurotransmitter transporter of a pre-synaptic Neuron after Cocaine is a dopamine transporter blocker that competitively inhibits dopamine uptake to increase the lifetime of dopamine and augments an overabundance of dopamine (an increase of up to 150 percent) within the parameters of the dopamine neurotransmitters. The Dopamine transporter (also dopamine active transporter DAT SLC6A3 is a membrane-spanning protein that binds the Neurotransmitter Dopamine

Like cocaine, amphetamines increase the concentration of dopamine in the synaptic gap, but by a different mechanism. Chemical synapses are specialized junctions through which Neurons signal to each other and to non-neuronal cells such as those in Muscles or Glands Amphetamines are similar in structure to dopamine, and so can enter the terminal button of the presynaptic neuron via its dopamine transporters as well as by diffusing through the neural membrane directly. By entering the presynaptic neuron, amphetamines force dopamine molecules out of their storage vesicles and expel them into the synaptic gap by making the dopamine transporters work in reverse.

Incentive salience

Main article: Incentive salience

Dopamine's role in experiencing pleasure has been questioned by several researchers. Incentive salience occurs when stimuli associated with drug -taking behavior begin reinforcing themselves It has been argued that dopamine is more associated with anticipatory desire and motivation (commonly referred to as "wanting") as opposed to actual consummatory pleasure (commonly referred to as "liking"). Dopamine is not released when unpleasant or aversive stimuli are encountered, in effect enhancing the pleasure of avoidance or removal of the unpleasant stimuli.

Dopamine, learning, and reward-seeking behavior

Dopaminergic neurons of the midbrain are the main source of dopamine in the brain. ^[9] Dopamine has been shown to be involved in the control of movements, the signaling of error in prediction of reward, motivation, and cognition. Cerebral dopamine depletion is the hallmark of Parkinson's disease. ^[9] Other pathological states have also been associated with dopamine dysfunction, such as schizophrenia, autism, and attention deficit hyperactivity disorder in children, as well as drug abuse. Dopamine is closely associated with reward-seeking behaviors, such as approach, consumption, and addiction. ^[9] Recent researches suggest that the firing of dopaminergic neurons is a motivational substance as a consequence of reward-anticipation. This hypothesis is based on the evidence that, when a reward is greater than expected, the firing of certain dopaminergic neurons increases, which consequently increases desire or motivation towards the reward. ^[9]

Animal studies

Clues to dopamine's role in motivation, desire, and pleasure have come from studies performed on animals. In one such study, rats were depleted of dopamine by up to 99 percent in the nucleus accumbens and neostriatum using 6-hydroxydopamine. The nucleus accumbens (NAcc also known as the accumbens nucleus or as the nucleus accumbens septi (Latin for nucleus leaning against the Septum The striatum is a subcortical (ie inside rather than on the outside part of the Telencephalon. ^[9] With this large reduction in dopamine, the rats would no longer eat by their own volition. The researchers then force-fed the rats food and noted whether they had the proper facial expressions indicating whether they liked or disliked it. The researchers of this study concluded that the reduction in dopamine did not reduce the rat's consummatory pleasure, only the desire to actually eat. In another study, mutant hyperdopaminergic (increased dopamine) mice show higher "wanting" but not "liking" of sweet rewards. ^[10]

The effects of drugs that reduce dopamine levels in humans

In humans, however, drugs that reduce dopamine activity (neuroleptics, e. Antipsychotics are a group of Psychoactive drugs commonly but not exclusively used to treat Psychosis, which is typified by Schizophrenia. g. some antipsychotics) have been shown to reduce motivation, and to cause anhedonia a. Antipsychotics are a group of Psychoactive drugs commonly but not exclusively used to treat Psychosis, which is typified by Schizophrenia. In Psychology, anhedonia ( Greek αν- an- without + ηδονή hēdonē pleasure) is an inability to experience k. a. the inability to experience pleasure. ^[11] Selective D2/D3 agonists pramipexole and ropinirole, used to treat Restless legs syndrome, have limited anti-anhedonic properties as measured by the Snaith-Hamilton Pleasure Scale. Pramipexole ( INN, trade names Mirapex and Sifrol) is a Medication indicated for treating Parkinson's disease and Restless legs Ropinirole (marketed under the brand names Requip and Ropark, in Extended release form as Requip XL) is a non- Ergoline Dopamine Restless legs syndrome (RLS Wittmaack-Ekbom's syndrome, or sometimes but inaccurately referred to as Nocturnal myoclonus) is a condition that is characterized ^[12] (The Snaith-Hamilton-Pleasure-Scale (SHAPS), introduced in English in 1995, assesses self-reported anhedonia in psychiatric patients. In Psychology, anhedonia ( Greek αν- an- without + ηδονή hēdonē pleasure) is an inability to experience ) These drugs have such side-effects as hypersexuality and compulsive gambling which are pleasure-determined effects of dopamine. Side Effect were an influential Disco band that recorded between 1972 and 1995 Hypersexuality is the desire to engage in Human sexual behavior at a level high enough to be considered clinically significant Problem gambling (ludomania is an urge to gamble despite harmful negative consequences or a desire to stop

Additionally, users of stimulants often have depleted dopamine levels after withdrawal from these addictive substances. Stimulant drugs are Drugs that temporarily increase alertness and awareness Withdrawal, also known as withdrawal/abstinence syndrome, refers to the characteristic signs and symptoms that appear when a drug that causes Physical dependence is

Opioid and cannabinoid transmission

Opioid and cannabinoid transmission instead of dopamine may modulate consummatory pleasure and food palatability (liking). An opioid is a chemical Substance that has a Morphine -like action in the body Cannabinoids ( are a group of terpeno[[phenol]]ic compounds present in Cannabis ( Cannabis sativa L ^[13] This could explain why animals' "liking" of food is independent of brain dopamine concentration. Other consummatory pleasures, however, may be more associated with dopamine. One study found that both anticipatory and consummatory measures of sexual behavior (male rats) were disrupted by DA receptor antagonists. ^[14] Libido can be increased by drugs that affect dopamine, but not by drugs that affect opioid peptides or other neurotransmitters.

Sociability

Sociability is also closely tied to dopamine neurotransmission. Low D2 receptor-binding is found in people with social anxiety. Social Phobia Social anxiety is a term used to describe an experience of Anxiety ( Emotional discomfort Fear, apprehension or Worry Traits common to negative schizophrenia (social withdrawal, apathy, anhedonia) are thought to be related to a hypodopaminergic state in certain areas of the brain. Solitude is a state of Seclusion or Isolation, ie lack of contact with people or love In Psychology, anhedonia ( Greek αν- an- without + ηδονή hēdonē pleasure) is an inability to experience In instances of bipolar disorder, manic subjects can become hypersocial, as well as hypersexual. Mania (from Greek μανία and that from μαίνομαι - mainomai, "to rage to be furious" is a severe medical condition Hypersexuality is the desire to engage in Human sexual behavior at a level high enough to be considered clinically significant This is also credited to an increase in dopamine, because mania can be reduced by dopamine-blocking anti-psychotics.

Processing of pain

Dopamine is also released according to the amount of pain a person is in, according to a study from the University of Michigan. ^[15] In the mesolimbic system's nucleus accumbens, an area also activated by pleasure, the activation corresponded exclusively with the subjective reported emotional response of the pain; while the caudate nucleus and the putamen were activated corresponding to the subjective reported sensory and affective qualities of the pain. The nucleus accumbens (NAcc also known as the accumbens nucleus or as the nucleus accumbens septi (Latin for nucleus leaning against the Septum The caudate nucleus is a nucleus located within the Basal ganglia of the Brains of many animal species "Putamen" is also a botanical term for the stone in a Fruit, such as a Peach. The basal ganglia's various sections activation during both, or either, pleasure and/or pain agrees with its overall role of determining the salience of stimuli. The basal ganglia (or basal nuclei) are a group of nuclei in the Brain interconnected with the Cerebral cortex, Thalamus and

Salience

Dopamine may also have a role in the salience ('noticeableness') of perceived objects and events, with potentially important stimuli such as: 1) rewarding things or 2) dangerous or threatening things seeming more noticeable or important. This article is about salience in the field of neuroscience for other meanings see Salience. ^[16] This hypothesis argues that dopamine assists decision-making by influencing the priority, or level of desire, of such stimuli to the person concerned.

Behavior disorders

Pharmacological blockade of brain dopamine receptors increases rather than decreases drug-taking behavior. Pharmacology (from Greek grc φάρμακον pharmakon, "drug" and grc -λογία -logia) is the study of how Drugs Since blocking dopamine decreases desire, the increase in drug-taking behaviour may be seen as not a chemical desire but as a deeply psychological desire to just 'feel something'.

Deficits in dopamine levels are implicated in attention-deficit hyperactivity disorder (ADHD), and stimulant medications used to successfully treat the disorder increase dopamine neurotransmitter levels, leading to decreased symptoms. Attention-Deficit Hyperactivity Disorder (ADHD is a neurobehavioral developmental disorder affecting about 3-5% of the world's population

Latent inhibition and creative drive

Dopamine in the mesolimbic pathway increases general arousal and goal directed behaviors and decreases latent inhibition; all three effects increase the creative drive of idea generation. The mesolimbic pathway is one of the Neural pathways in the Brain that links the Ventral tegmentum in the Midbrain to the Nucleus accumbens Arousal is a physiological and psychological state of being awake Latent inhibition is a process by which exposure to a stimulus of little or no consequence prevents conditioned associations with that stimulus being formed This has led to a three-factor model of creativity involving the frontal lobes, the temporal lobes, and mesolimbic dopamine. Creativity is a mental process involving the generation of new Ideas or Concepts, or new associations of the creative mind between existing ideas or concepts The frontal lobe is an area in the Brain of Mammals It is located at the front of each Cerebral hemisphere and positioned anterior to (in front of the The temporal lobes are parts of the cerebrum that are involved in speech, Memory, and Hearing. ^[17]

Links to psychosis

Main article: Dopamine hypothesis of psychosis

Abnormally high dopamine action has also been strongly linked to psychosis and schizophrenia,^[18] Dopamine neurons in the mesolimbic pathway are particularly associated with these conditions. The dopamine hypothesis of schizophrenia or the dopamine hypothesis of psychosis is a model attributing symptoms of Schizophrenia (like psychoses) to a Psychosis (from the Greek ψυχή "psyche" for mind or soul and -οσις "-osis" for abnormal condition with adjective psychotic Schizophrenia ( from the Greek roots schizein (σχίζειν "to split" and phrēn The mesolimbic pathway is one of the Neural pathways in the Brain that links the Ventral tegmentum in the Midbrain to the Nucleus accumbens Evidence comes partly from the discovery of a class of drugs called the phenothiazines (which block D₂ dopamine receptors) that can reduce psychotic symptoms, and partly from the finding that drugs such as amphetamine and cocaine (which are known to greatly increase dopamine levels) can cause psychosis. Phenothiazine is the Organic compound with the formula S(C6H42NH Dopamine receptors are a class of metabotropic G protein-coupled receptors that are prominent in the Vertebrate Central nervous system (CNS Amphetamine, and related drugs such as Methamphetamine are a group of drugs that act by increasing levels of Norepinephrine, Serotonin, and Dopamine Cocaine ( benzoylmethyl ecgonine) is a Crystalline Tropane Alkaloid that is obtained from the leaves of the Coca plant ^[19] Because of this, most modern antipsychotic medications, for example, Risperidone, are designed to block dopamine function to varying degrees. Antipsychotics are a group of Psychoactive drugs commonly but not exclusively used to treat Psychosis, which is typified by Schizophrenia. Risperidone (pronounced Ris-PER-ǐ-dōn and sold under the trade name Risperdal in the Netherlands, United States, Canada, the

Therapeutic use

Main article: L-DOPA

Levodopa is a dopamine precursor used in various forms to treat Parkinson's disease and dopa-responsive dystonia. Parkinson's disease (also known as Parkinson disease or PD) is a degenerative disorder of the Central nervous system that often impairs the sufferer's Dystonia is a neurological Movement disorder in which sustained muscle contractions cause twisting and repetitive movements or abnormal postures It is typically co-administered with an inhibitor of peripheral decarboxylation (DDC, dopa decarboxylase), such as carbidopa or benserazide. Aromatic L-amino acid decarboxylase ( synonyms DOPA decarboxylase Tryptophan Decarboxylase, 5-hydroxytryptophan decarboxylase AAAD is a Lyase Carbidopa (MK-486 tradename Lodosyn) is a drug given to people with Parkinson's disease in order to inhibit peripheral Metabolism of Levodopa Benserazide (also called Serazide or Ro 4-4602 is a DOPA decarboxylase inhibitor which is unable to cross the Blood-brain barrier. Inhibitors of alternative metabolic route for dopamine by catechol-O-methyl transferase are also used. Catechol- O -methyl transferase ( COMT;) is one of several Enzymes that degrade Catecholamines such as Dopamine, Epinephrine These include entacapone and tolcapone. Entacapone ( INN) (ˌɛntəkəˈpoʊn/ /ɛnˈtækəpoʊn Tolcapone is a Drug that inhibits the Enzyme Catechol-O-methyl transferase (COMT

Dopamine is also used as an inotropic drug in patients with shock to increase cardiac output and blood pressure. An inotrope (ˈaɪnətroʊp is an agent that alters the force or energy of Muscular contractions Negatively inotropic agents weaken the force of muscular contractions Cardiac output (Q is the volume of blood being pumped by the Heart, in particular by a ventricle in a minute Blood pressure is also the title of a short story by Damon Runyan in Guys and Dolls and Other Stories The effects of dopamine, also known as Intropin, are dose dependent. Dosages from 2 mcg/kg/min to 5 mcg/kg/min are considered the "renal dose. " This dosage level causes blood vessels within the kidneys to dilate, increasing the effectiveness of the kidneys, and potentially increasing urine output. from 5 mcg/kg/min to 10 mcg/kg/min is the inotropic dose, meaning it causes the myocardium to contract with greater force, thus increasing blood pressure. An inotrope (ˈaɪnətroʊp is an agent that alters the force or energy of Muscular contractions Negatively inotropic agents weaken the force of muscular contractions Myocardium is the muscular tissue of the Heart. Relationship to other layers The other tissues of the heart are the Endocardium It will also increase heart rate, and thus cardiac output. From 10 mcg/kg/min to 20 mcg/kg/min is the "pressor" dose. This dose causes the greatest level of vasoconstriction, increases blood pressure and heart rate the most, but can cause the vessels in the kidneys to constrict to the point where they will become non functional. This dose also greatly increases systemic vascular resistance. Vascular resistance is a term used to define the resistance to flow that must be overcome to push Blood through the Circulatory system.

Dopamine and fruit browning

Polyphenol oxidases (PPOs) are a family of enzymes responsible for the browning of fresh fruits and vegetables when they are cut or bruised. Polyphenol oxidase (PPO enzymes catalyse the o -hydroxylation of monophenols ( Phenol molecules in which the benzene ring contains a single Hydroxyl Browning is the process of becoming Brown, especially referring to Food. These enzymes use molecular oxygen (O₂) to oxidise various 1,2-diphenols to their corresponding quinones. Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the Redox (shorthand for reduction-oxidation reaction describes all Chemical reactions in which atoms have their Oxidation number ( Oxidation state Benzenediols or dihydroxybenzenes are Aromatic Chemical compounds and Polyphenols in which two Hydroxyl groups are substituted onto a "DDQ" redirects here DDQ is also the former callsign of a TV station in Toowoomba Queensland Australia The natural substrate for PPOs in bananas is dopamine. For the fruit see Banana. For other meanings see Banana (disambiguation. The product of their oxidation, dopamine quinone, spontaneously oxidises to other quinones. The quinones then polymerise and condense with amino acids and proteins to form brown pigments known as melanins. In Polymer chemistry, polymerization is a process of reacting Monomer Molecules together in a Chemical reaction to form three-dimensional networks Condensation is the change of the physical state of aggregation (or simply state of matter from gaseous phase into liquid phase In Chemistry, an amino acid is a Molecule containing both Amine and Carboxyl Functional groups In Biochemistry, this Proteins are large Organic compounds made of Amino acids arranged in a linear chain and joined together by Peptide bonds between the Carboxyl In Biology, a pigment or biochrome is any material resulting in Color of plant or animal cells which Melanin is a class of compounds found in the Plant, Animal and Protista kingdoms, where it serves predominantly as a Pigment. The quinones and melanins derived from dopamine may help protect damaged fruit and vegetables against growth of bacteria and fungi. The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have A fungus (ˈfʌŋgəs is a eukaryotic Organism that is a member of the kingdom Fungi (ˈfʌndʒaɪ ^[20]

References

See also

External links

• DrugBank APRD00085

The term " addiction " is used in many contexts to describe an obsession compulsion or excessive Physical dependence or psychological dependence such as Amphetamine, and related drugs such as Methamphetamine are a group of drugs that act by increasing levels of Norepinephrine, Serotonin, and Dopamine Antipsychotics are a group of Psychoactive drugs commonly but not exclusively used to treat Psychosis, which is typified by Schizophrenia. Catechol- O -methyl transferase ( COMT;) is one of several Enzymes that degrade Catecholamines such as Dopamine, Epinephrine Classical Conditioning (also Pavlovian or Respondent Conditioning) is a form of Associative learning that was first demonstrated by Ivan Pavlov Cocaine ( benzoylmethyl ecgonine) is a Crystalline Tropane Alkaloid that is obtained from the leaves of the Coca plant In the fields of Psychology and Psychiatry, the terms depression or depressed refer to both expected and pathologically chronic or severe The dopamine hypothesis of schizophrenia or the dopamine hypothesis of psychosis is a model attributing symptoms of Schizophrenia (like psychoses) to a Dopamine Reuptake Inhibitors ( DARI) Dopamine Uptake Inhibitors, Dopamine Transporter Inhibitors are compounds that inhibit the Reuptake of extracellular See Chemical synapse for an introduction to concepts and terminology used in this article Parkinson's disease (also known as Parkinson disease or PD) is a degenerative disorder of the Central nervous system that often impairs the sufferer's A prolactinoma is a Benign Tumor ( Adenoma) of the Pituitary gland that produces a Hormone called Prolactin. Schizophrenia ( from the Greek roots schizein (σχίζειν "to split" and phrēn Selegiline (l-deprenyl Eldepryl Zelapar or Anipryl Veterinary) is a drug used for the treatment of early-stage Parkinson's disease, Depression Serotonin (ˌsɛrəˈtoʊnən ( 5-hydroxytryptamine, or 5-HT) is a Monoamine Neurotransmitter synthesized in serotonergic Neurons The DrugBank database available at the University of Alberta is a unique Bioinformatics and Cheminformatics resource that combines detailed drug (i

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