|
Introduction
of Dopamine
Dopamine is a
phenethylamine naturally produced by the human body. In the
brain, dopamine functions as a neurotransmitter, activating
the five types of dopamine receptor - D1, D2, D3, D4 and D5,
and their variants. Dopamine is produced in several areas of
the brain, including the substantia nigra.
Dopamine is also a neurohormone released by the hypothalamus.
Its main function as a hormone is to inhibit the release of
prolactin from the anterior lobe of the pituitary.
Dopamine can be supplied as a medication that acts on the
sympathetic nervous system, producing effects such as
increased heart rate and blood pressure. However, since
dopamine cannot cross the blood-brain barrier, dopamine given
as a drug does not directly affect the central nervous system.
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.
History of Dopamine
Dopamine was discovered by Arvid Carlsson and Nils-Åke Hillarp
at the Laboratory for Chemical Pharmacology of the National
Heart Institute of Sweden, in 1952. It was named Dopamine
because it was a monoamine, and its synthetic precursor was
3,4-dihydroxyphenylalanine (L-DOPA). Arvid Carlsson was
awarded the 2000 Nobel Prize in Physiology or Medicine for
showing that dopamine is not just a precursor of noradrenaline
and adrenaline, but a neurotransmitter as well.
Biochemistry of Dopamine
Dopamine has the
chemical formula (C6H3(OH)2-CH2-CH2-NH2). Its chemical name is
4-(2-aminoethyl)benzene-1,2-diol and it is abbreviated "DA."
As a member of the catecholamine family, dopamine is a
precursor to epinephrine (adrenaline) and then norepinephrine
(noradrenaline) in the biosynthetic pathways for these
neurotransmitters.
Dopamine is biosynthesized in the body (mainly by nervous
tissue and adrenal glands) first by the hydration of the amino
acid L-tyrosine to L-DOPA via the enzyme tyrosine
3-monooxygenase, which is often known by its former name
tyrosine hydroxylase, and then by the decarboxylation of DOPA
by Aromatic L-amino acid decarboxylase (which is often
referred to as dopa decarboxylase). In neurons, dopamine is
packaged after synthesis into vesicles, which are then
released in response to the presynaptic action potential. The
inactivation mechanism of neurotransmission are 1) uptake via
a specific transporter; 2) enzymatic breakdown; and 3)
diffusion. Uptake back to the presynaptic neuron via the
dopamine transporter is the major role in the inactivation of
dopamine neurotransmission. The recycled dopamine will face
either breakdown by an enzyme or be re-packaged into vesicles
and reused.
Disclaimer:
Information on this page is provided for general
information purposes. You should not make a clinical treatment
decision based on information contained in this page without
consulting other references including the package insert of
the drug, textbooks and where relevant, expert opinion. We
cannot be held responsible for any errors you make in
administering drugs mentioned on this page, nor for use of any
erroneous information contained on this page.
|
