Restless legs syndrome and attention deficit hyperactivity disorder (ADHD) are associated with decreased dopamine activity. Similar dopamine antagonist drugs are also some of the most effective anti-nausea agents. 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. Its metabolic precursor L-DOPA can be manufactured Levodopa, a pure form of L-DOPA, is the most widely used treatment for Parkinson's. 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. 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 the effects of dopamine. 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. In blood vessels, it inhibits norepinephrine release and acts as a vasodilator (at normal concentrations) 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. Outside the central nervous system, dopamine functions primarily as a local paracrine messenger. 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 the organism's behavior toward or away from achieving that outcome. These pathways and cell groups form a dopamine system which is neuromodulatory. Other brain dopamine pathways are involved in motor control and in controlling the release of various hormones.
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. The brain includes several distinct dopamine pathways, one of which plays a major role in the motivational component of reward-motivated behavior. Neurotransmitters are synthesized in specific regions of the brain, but affect many regions systemically. In the brain, dopamine functions as a neurotransmitter-a chemical released by neurons (nerve cells) to send signals to other nerve cells.
Dopamine is also synthesized in plants and most animals. 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 constitutes about 80% of the catecholamine content in the brain. It is an organic chemical of the catecholamine and phenethylamine families. Dopamine ( DA, a contraction of 3,4- dihydr oxy phenethyl amine) is a neuromodulatory molecule that plays several important roles in cells.
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