Table of Contents
Dopamine
Dopamine is classified as a catecholamine (a group of biologically active substances that act as neurotransmitters and hormones) and is a precursor (precursor) of adrenaline and noradrenaline. It is formed by the decarboxylation (separation of the carboxyl group COOH) of L-DOPA. Dopamine is responsible for a number of important functions in the human body. Fluctuations in its levels can lead to more serious disease states – neurological, mental, related to motility.
History
Dopamine was first synthesized in 1910 by George Barger and James Ewens at Wellcome Laboratories in London. Its function as a neurotransmitter was discovered in 1958 by Arvid Carlsson and Nils-Åke Hillarp, National Heart Institute, Sweden. It has the chemical formula C6H3 (OH) 2-CH2-CH2-NH2, and its chemical name is 4- (2-aminoethyl) benzene-1,2-diol. Abbreviated “DA”.
Biosynthesis
It is synthesized in the body first by the hydroxylation (formation of phenols) of the amino acid L-tyrosine (l-tyrosine) in l-dopa (Levodopa) using the enzyme tyrosine hydroxylase. This is followed by decarboxylation (conversion) of Levodopa to dopamine by the aromatic amino acid decarboxylase, or dopa decarboxylase. In some neurons, dopamine is converted to dorepinephrine by the enzyme dopamine beta-hydroxylase.
Functions
Dopamine is produced in several areas of the brain, including the substance nigra (Latin for “black substance”, located in the middle part of the brain and responsible for behavior, movement and dependence) and VTA (Ventral tegmental area – a group of neurons located in The area is responsible for substance addiction, behavioral regulation, motivation, cognition, and certain mental disorders).
Regulation of prolactin secretion
Dopamine is a neurohormone that is released from the hypothalamus – a structure in the brain that controls body temperature, feelings of hunger and thirst, fatigue, sleep and circadian (circadian) rhythms. Circadian rhythms are hereditary and are generated in the body by a specialized system known as the “biological clock”. Its main function as a hormone is to suppress the release of prolactin from the anterior pituitary gland.
Prolactin (PRL or LTH) is responsible for the secretion of milk in the mammary glands (breastfeeding). The pituitary gland is the main endocrine gland, and the hormones secreted by it control certain processes in the body such as growth, blood pressure, water balance in the body, milk production and more.
Movement (motility)
Dopamine has several receptors – D1-5 and their variants. They are responsible for various processes such as cognitive activity, volitional movements, motivation, pleasures, memory. Through them and the constant maintenance of dopamine activity in the basal ganglia (located under the cerebral cortex and responsible for the regulation of various motor and mental processes) involuntary movements are prevented. Dopamine synthesis deficiency can cause Parkinson’s disease, which is characterized by the inability to perform controlled movements.
Motivation and dependencies
Dopamine binds to that part of the brain that provides the feeling of pleasure. Dopamine is released through food, sex, drugs. Thus, addictions to cocaine, heroin, nicotine, caffeine can be explained. In these cases, there is over-motivation – increased readiness to react. Addiction is associated with increased sensitivity of dopamine D1 receptors. Short-term fluctuations in dopamine activity are associated with mental processes such as motivation and concentration. When it is very low, a person is prone to depression – one of the main symptoms is low motivation.
Cognitive ability
In the frontal lobe of the brain, dopamine controls the flow of information from other parts of the brain. Dopamine disorders in this area can cause deterioration of some neurocognitive functions such as memory, attention and problem solving. The receptors responsible for the effect on cognition are D1 and D4.
Treatment
Dopamine can be delivered as a treatment that affects the sympathetic nervous system (part of the autonomic nervous system, which is responsible for a number of vital processes such as blood circulation, respiration, digestion, etc.), increasing heart rate and blood pressure. It is used in patients with Parkinson’s syndrome and vegetative-vascular dystonia by taking levodopa. Dopamine alone cannot cross the blood-brain barrier, and its precursor levodopa passes through it relatively easily.
The blood-brain barrier separates the blood circulation from the cerebrospinal fluid through many cells and capillaries, is responsible for maintaining a relatively constant environment for the normal functioning of the brain – through it enter the substances necessary for its work and remove toxins and other waste products.
Diseases and side effects due to changes in dopamine activity
Dopamine is extremely important because as a neurotransmitter it is involved in the regulation of various processes in the central and peripheral nervous system. Too low or high dopamine activity is the cause of a number of diseases – neurological and mental, some of which are irreversible.
- Parkinson’s disease – a neurological disease characterized by difficulty or inability to move, tremors (involuntary contraction and relaxation of a muscle group) and others. The cause is degeneration (a change in the structure of cells, tissues and organs, which reduces their viability) in the central nervous system and in particular the death of cells that produce dopamine in the substance nigra. The reason for this is still unclear.
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Schizophrenia – psychosis, which is characterized by various symptoms (delirium, hallucinations, paranoia, etc.). It is caused by too high dopamine activity and is treated with antipsychotic drugs.
On the other hand, antipsychotic or neuroleptic drugs such as dopamine suppressants have a number of side effects with long-term use. They reduce concentration, limit motivation and make it impossible to experience pleasure.
May cause:
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Dyskinesia – involuntary movement disorder;
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Impaired function of the male and female gonads. In women, they reduce the levels of estradiol and progesterone, and in men – lower the levels of testosterone and dhea (DeHydroEpiAndrosterone, a hormone that increases testosterone levels in the blood and respectively leads to an increase in muscle mass and strength);
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Amenorrhea;
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Loss of libido;
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False positive results in pregnancy tests;
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Risk of osteoporosis in women;
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Gynecomastia and impotence in men;
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Weight gain;
- Diabetes; Strong salivation;
- Dysphoria – the opposite of euphoria, a disease characterized by depression, dark thoughts and dissatisfaction;
- Fatigue; Heart rhythm problems, heart attack, etc .;
- Tired legs syndrome – a condition in which you feel pain, itching, tingling in the limbs, as well as heaviness, fatigue and tension. It most often affects the legs, but it is possible to affect the upper limbs;
- Fibromyalgia – a rheumatic disease with muscle and joint pain. The reason is a violation of the function of dopamine as a neurotransmitter and its absence in some organs. As a hormone from the group of catecholamines (which includes adrenaline and noradrenaline), it has a analgesic role.
