Dopamine metabolism (Homo sapiens)

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Dopamine is an organic chemical of the catecholamine and phenethylamine families that plays several important roles in the brain and body. 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.

The dopamine system plays a central role in several significant medical conditions, including Parkinson's disease. Parkinson's disease is an age-related disorder characterized by movement disorders such as stiffness of the body, slowing of movement, and trembling of limbs when they are not in use. The main symptoms are caused by the loss of dopamine-secreting cells in the substantia nigra. These dopamine cells are especially vulnerable to damage, and a variety of insults, including encephalitis (as depicted in the book and movie "Awakenings"), repeated sports-related concussions, and some forms of chemical poisoning such as MPTP, can lead to substantial cell loss, producing a parkinsonian syndrome that is similar in its main features to Parkinson's disease. The most widely used treatment for parkinsonism is administration of L-DOPA, the metabolic precursor for dopamine. L-DOPA is converted to dopamine in the brain and various parts of the body by the enzyme DOPA decarboxylase.[14] L-DOPA is used rather than dopamine itself because, unlike dopamine, it is capable of crossing the blood-brain barrier.

Description source: Wikipedia