Dopamine is a neurotransmitter hormone produced mainly by the brain and which acts by transmitting information created by the nervous system.
This messenger of our body, when released, mainly produces the feeling of well being.
Dopamine: what it is and what it does in our body
Dopamine is a biogenic amine in the catecholamine group, as it is produced from the decarboxylation of the amino acid tyrosine.
It is a chemical compound, whose name by IUPAC is 3,4-dihydroxy-phenylethanamine and has a molecular formula is C 8 H 11 NO 2 .
This neurotransmitter acts in our body by signaling and transporting information between the nervous system and also to different parts of the body.
The main functions of dopamine in our body are:
- Improves memory, mood, cognition and attention
- Stimulates feelings of well-being and pleasure
- Controls appetite, sleep, mental and motor functions
- Combats anxiety and depression
- Related to the ability to overcome challenges (motivation)
Some diseases are associated with abnormal levels (high or low rates) of dopamine such as the degenerative disease called Parkinson’s disease, as the nerve cells that produce the substance age.
Dopamine synthesis and release in the body
Dopamine is biosynthesized from the amino acid tyrosine. The body sites where dopamine synthesis occurs are: adrenal gland and in four regions of the brain: nigrostriatal, mesolimbic, mesocortical and tuberofundibular.
The dopamine precursor amino acid, tyrosine, is obtained through food and produced in small amounts in the liver through phenylalanine.
Dopamine production begins with the conversion of tyrosine (4-hydroxyphenylalanine) to L-dopa (L-3,4-dihydroxyphenylalanine) by the action of the enzyme tyrosine hydroxylase causing oxidation of the compound to occur.
L-dopa, in turn, has a carboxyl group removed to produce dopamine, catalyzed by the aromatic amino acid enzyme decarboxylase. Dopamine (3,4-dihydroxy-phenylethanamine) is the final synthesis product of catecholamines in dopaminergic neurons.
Once produced, dopamine is transported from the cytoplasm and stored in intracellular vesicles. The release occurs by stimulation of the nerve cell and the neurotransmitter passes to the synaptic space through exocytosis.
In the body, dopamine is released during exercise, meditation, the sexual act and even when we are eating something appetizing.
Dopaminergic system and dopaminergic receptors
According to studies, the dopaminergic system is related to the desire to eat, as it acts by triggering the sensation of pleasure when receiving natural rewards, such as food.
There are 5 types of dopaminergic receptors. They are: Class D1 (D1 and D5) and Class D2 (D2, D3 and D4). These classes are receptor proteins coupled to the G protein.
D1 and D5 are stimulatory receptors, that is, they have an activating effect on the cell, as they will stimulate cellular function and trigger different responses in each tissue of the body. D2, D3 and D4, on the other hand, act as inhibitors, since they decrease cell levels.
See these examples of action: while D1 can act to stimulate appetite, causing the person to eat more, D2 can inhibit the desire to consume food, as it indicates that the person is already satiated.
Dopaminergic receptors are distributed in different ways in the brain. Examples of regions where the presence of receptors are observed are: striatum (D1), adenohypophysis lactotrophs (D2), limbic system (D3), frontal cortex (D4) and hippocampus (D5).
Dopaminergic pathways: location and performance of dopamine
The four main dopaminergic pathways cause dopamine to develop its different functions in the body. Are they:
The mesolimbic pathway comprises the ventral tegmental area (ATV) axis of the midbrain-limbic system and is related to reinforcement and stimulation, that is, dopamine is sent when the individual is exposed to situations of pleasure and reward.
The mesocortical pathway connects the ventral tegmental area (VTA) of the midbrain to the frontal lobes of the cerebral cortex and is related to attention, cognition and orientation.
The nigrostriatal pathway is the pathway that contains 80% of dopamine in the brain and that stimulate voluntary movements, that is, locomotion and movement. The onset occurs in the substantia nigra of the brain and the axis extends to the glands of the base.
The tuberoinfundibular pathway comprises the hypothalamus-pituitary axis and dopamine regulates prolactin, a hormone related to milk production that also acts on metabolism, sexual satisfaction and the immune system.
Neurotransmitters: dopamine, serotonin, adrenaline and norepinephrine
Dopamine, serotonin, adrenaline and norepinephrine are biogenic amines, that is, organic compounds whose structures contain the nitrogen element and which are produced by the body.
Dopamine, adrenaline and norepinephrine are part of catecholamines , because they have the catechol radical in their structure, being derived from the amino acid tyrosine and produced in sympathetic nerve endings.
Since the serotonin is a indoleamine due to the presence of indole is synthesized from radical carboxylation and hydroxylation of the amino acid tryptophan in serotonergic neurons.
Dopamine results from the oxidation of tyrosine, converting it to L-dopa and, subsequently, the decarboxylation of the compound that promotes the appearance of dopamine occurs.
Dopamine is stored in the synaptic vesicles of dopaminergic neurons. The dopamine hydroxylase enzyme converts dopamine to noradrenaline in adrenergic and noradrenergic neurons.
Methylation of norepinephrine causes adrenaline to be produced in the adrenal medulla and some neurons.
History of dopamine and medicinal use
Dopamine was synthesized in the laboratory at the beginning of the 20th century, by the English scientist George Barger (1878-1939). Later, in 1958, Swedish chemists Arvid Carlsson and Nils-Ake Hillarp, discovered functions attributed to this substance, mainly as a neurotransmitter.
Dopamine is used as a therapeutic target in disorders of the central nervous system, results of its decrease, such as Parkinson’s disease and schizophrenia.
Many psychoactive drugs are associated with dopamine release, and therefore, with chemical dependency (addiction).