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Transcript of Dopamine
Introduction to Dopamine
Diseases and disorders
Dopamine has been demonstrated to play a role in pain processing in multiple levels of the central nervous system. Accordingly, decreased levels of dopamine have been associated with painful symptoms that frequently occur in Parkinson's disease. Abnormalities in dopaminergic neurotransmission have also been demonstrated in painful clinical conditions, including burning mouth syndrome,fibromyalgia, and restless legs syndrome.
Dopaminergic system of body
Outside the nervous system, dopamine functions in several parts of the body as a local chemical messenger. In the 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 the immune system it reduces the activity of lymphocytes. With the exception of the blood vessels, dopamine in each of these peripheral systems has a "paracrine" function: it is synthesized locally and exerts its effects on cells that are located near the cells that release it.
Dopamine has many functions in the brain, including important roles in behavior and cognition, voluntary movement, motivation, punishment and reward, inhibition of prolactin production (involved in lactation and sexual gratification), sleep, dreaming, mood, attention, working memory, and learning. Dopaminergic neurons (i.e., neurons whose primary neurotransmitter is dopamine) are present chiefly in the ventral tegmental area (VTA) of the midbrain, the substantia nigra, and the arcuate nucleus of the hypothalamus.
*In the brain
Dopamine is commonly associated with the reward system of the brain, providing feelings of enjoyment and reinforcement to motivate a person to perform certain activities. Dopamine is released by rewarding experiences such as food, sex, drugs, and neutral stimuli that become associated with them.Recent studies indicate that aggression may also stimulate the release of dopamine in this way.
Kent Berridge and other researchers have argued for a distinction between reward, which is defined in terms of motivation, and pleasure, which is defined in terms of emotional expression. A simpler way of describing this is as a distinction between "seeking" and "liking". "Seeking" occurs when an animal, given access to some stimulus such as food, executes some type of active behavior in order to acquire it. "Liking" occurs when an animal shows expressions of happiness or satisfaction while consuming something. There is considerable evidence that the dopamine system is part of the brain system that mediates seeking but not part of the system that mediates liking. Animals in which the VTA 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 facial expressions indicative of pleasure.
Seeking v.s Liking
Role in cognition
Attention deficit hyperactivity disorder
Altered dopamine neurotransmission is implicated in attention deficit hyperactivity disorder (ADHD), a condition associated with impaired ability to regulate attention, behavior, and/or impulses. There are some genetic links between dopamine receptors, the dopamine transporter and ADHD, in addition to links to other neurotransmitter receptors and transporters. The most important relationship between dopamine and ADHD involves the drugs that are used to treat ADHD. Some of the most effective therapeutic agents for ADHD are psychostimulants such as methylphenidate and amphetamine, drugs that increase both dopamine and norepinephrine levels in brain.
Abnormally high dopaminergic transmission has been linked to psychosis and schizophrenia. However, clinical studies relating schizophrenia to brain dopamine metabolism have ranged from controversial to negative. Increased dopaminergic functional activity, specifically in the mesolimbic pathway, is found in schizophrenic individuals. However, decreased activity in another dopaminergic pathway, the mesocortical pathway, may also be involved. The two pathways are thought to be responsible for differing sets of symptoms seen in schizophrenia.
Dopamine was first synthesized in 1910 by George Barger and James Ewens at Wellcome Laboratories in London, England.Dopamine's function as a neurotransmitter was first recognized in 1958 by Arvid Carlsson and Nils-Åke Hillarp at the Laboratory for Chemical Pharmacology of the National Heart Institute of Sweden. Carlsson was awarded the 2000 Nobel Prize in Physiology or Medicine for showing that dopamine is not only a precursor of norepinephrine (noradrenaline) and epinephrine (adrenaline), but also a neurotransmitter.
George Barger and James Ewens
Tommy & Mary!!
Dopamine's effects on higher
cognitive function have been studied in monkeys and rodents.
*Outside the nervous system
by Mary & Tommy
A substance that acts both as a neurotransmitter and hormone, secreted in the central nervous system, at the nerve endings of the sympathetic nervous system, and by the adrenal gland.
A hormone secreted by the adrenal medulla that is released into the bloodstream in response to physical or mental stress, as from fear or injury. It initiates many bodily responses, including the stimulation of heart action and an increase in blood pressure, metabolic rate, and blood glucose concentration.
Central Nervous System