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Dopamine


Synthesis, function and effect

The neurotransmitter dopamine (DA) belongs to the group of catecholamines as well as adrenaline and norepinephrine.
The synthesis of dopamine (C8H11NO2) takes place in the human organism in the dopaminergic nerve cells, of which the predominant part is in the substantia nigra, an area in the midbrain. Two enzymatic reactions turn the amino acid tyrosine (C9H11NO3) the neurotransmitter dopamine. Tyrosine hydroxylase hydroxilates tyrosine initially to levodopa (C9H11NO4). In the following step, DOPA decarboxylase decarboxylates levodopa to dopamine. By the way, both processes do not differ from the synthesis of the other two catecholamines norepinephrine and epinephrine.
For humans, dopamine is important in many ways. On the one hand, the general motor function (all movements) is controlled by dopamine. The neurotransmitter is responsible for the transmission of nerve cell excitation to the muscle cell.
On the other hand, dopamine in the reward system of the nucleus accumbens provides for happy and euphoric feelings. There is also a direct link between addiction and the dopaminergic reward system: a variety of drugs work in the human reward system, either by providing more dopamine (eg, amphetamines) or by preventing dopamine from reoccurring is degraded (eg in cocaine). The noise conditions thus caused have a high addictive potential.
In the field of research, deficiency or overflow situations of dopamine have been investigated for a long time. For example, lack of dopamine in the brain causes symptoms of Parkinson's disease, which is associated with numerous neurological dysfunctions such as muscle rigidity, tremors or slowed movements. By contrast, an excess supply of the neurotransmitter leads to hallucinatory states. Therefore, dopamine is closely suspected of causing schizophrenia (dopamine hypothesis).