Neurotransmitters, part 1

Dopamine, norepinephrine, serotonin

Atlas company blog, Geektimes

Neurotransmitters are a holiday that is always with you. We constantly hear that it is they who give feelings of joy and pleasure, but we know little about how they work. In the first part of a small educational course, Atlas talks about three of the most famous neurotransmitters, without which our life would be simply disgusting.

How Neurotransmitters work

Nerve cells communicate with each other using processes – axons and dendrites. There is a gap between them – the so-called synaptic gap. This is where the interaction of neurons takes place.

Mediators are synthesized in the cell and delivered to the end of the axon – to the presynaptic membrane. There, under the influence of electrical impulses, they enter the synaptic cleft and activate the receptors of the next neuron. After activation of the receptors, the neurotransmitter returns back to the cell (the so-called reuptake occurs) or is destroyed.

Neurotransmitters themselves are not proteins, so there is no "dopamine gene" or "adrenaline gene". Proteins do all the auxiliary work: enzyme proteins synthesize the neurotransmitter substance, transporter proteins are responsible for delivery, receptor proteins activate the nerve cell. Several proteins can be responsible for the correct operation of one neurotransmitter – which means several different genes.

Dopamine

Due to the activation of neurons in different areas of the brain, dopamine plays several roles. Firstly, it is responsible for motor activity and gives the joy of movement. Secondly, it gives a feeling of almost childish delight in learning new things – and the desire to search for novelty. Third, dopamine performs an important function of reward and motivation reinforcement: as soon as we do something useful for the life of the human species, the neurons give us a prize – a sense of satisfaction (sometimes called pleasure). At the basic level, we get a reward for simple human joys – food and sex, but in general, the options for achieving satisfaction depend on everyone's tastes – someone will get a "carrot" for the completed code, someone - for this article.

The reward system is connected with learning: a person gets pleasure, and new cause-and-effect associations are formed in his brain. And then, when the pleasure passes and the question arises how to get it again, there will be a simple solution – to write another article.

Dopamine looks like an excellent stimulant for work and study, as well as an ideal drug – it is with the action of dopamine that most drugs (amphetamine, cocaine) are associated, but there are serious side effects. An "overdose" of dopamine leads to schizophrenia (the brain works so actively that it begins to manifest itself in auditory and visual hallucinations), and a lack of it leads to a depressive disorder or the development of Parkinson's disease.

Dopamine has five receptors, numbered from D1 to D5. The fourth receptor is responsible for the search for novelty. It is encoded by the DRD4 gene, the length of which determines the intensity of dopamine perception. The fewer the number of repetitions, the easier it is for a person to reach the peak of pleasure. Such people will most likely have enough of a delicious dinner and a good movie.

The greater the number of repetitions – and there can be up to ten of them – the harder it is to have fun. Such people have to try to get a reward: go on a trip around the world, conquer the top of a mountain, do a somersault on a motorcycle or put the whole state on red in Las Vegas. This genotype is associated with the range of migration of ancient people from Africa across Eurasia. There are also sad statistics: The "unsatisfactory" variant of DRD4 is more common among those convicted of serious crimes in prisons.

Norepinephrine

Norepinephrine is a neurotransmitter of wakefulness and making quick decisions. It is activated under stress and in extreme situations, participates in the "fight or flight" reaction. Norepinephrine causes a surge of energy, reduces the feeling of fear, increases the level of aggression. At the somatic level, under the influence of norepinephrine, the heart rate increases and the pressure increases.

Noradrenaline is a favorite mediator of surfers, snowboarders, motorcyclists and other fans of extreme sports, as well as their colleagues in casinos and gaming clubs – the brain does not make a difference between real events and imaginary ones, so the risk of losing your fortune in cards is enough to activate noradrenaline.

A high level of norepinephrine leads to a decrease in vision and analytical abilities, and a lack of it leads to boredom and apathy.

The SLC6A2 gene encodes the norepinephrine transporter protein. It ensures the reuptake of norepinephrine into the presynaptic membrane. It depends on his work how long norepinephrine will act in the human body after he has successfully coped with a dangerous situation. Mutations in this gene can cause attention deficit disorder (ADHD).

Serotonin

We are used to hearing about it as a "hormone of happiness", while serotonin is not a hormone at all, and with "happiness" everything is not so clear. Serotonin is a neurotransmitter that does not so much bring positive emotions as it reduces susceptibility to negative ones. It supports the "neighboring" neurotransmitters – norepinephrine and dopamine; serotonin is involved in motor activity, reduces the overall pain background, helps the body in the fight against inflammation. Serotonin also increases the accuracy of transmitting active signals in the brain and helps to concentrate.

An overabundance of serotonin (for example, when using LSD) increases the "volume" of secondary signals in the brain, and hallucinations occur. Lack of serotonin and imbalance between positive and negative emotions are the main cause of depression.

The 5-HTTLPR gene encodes a serotonin transporter protein. The gene sequence contains a section of repeats, the number of which may vary. The longer the chain, the easier it is for a person to maintain a positive attitude and switch from negative emotions. The shorter it is, the higher the probability that a negative experience will be traumatic. The "long" variant of the gene is also associated with sudden infant mortality syndrome, aggressive behavior during the development of Alzheimer's disease and a tendency to depression.

Destruction of neurotransmitters

The action of neurotransmitters is like a holiday, as if everyone went out in a joyful crowd to watch the fireworks. But the holiday cannot (and should not) last forever, and neon roses in the night sky should give way to the usual constellations and the dawn.For this, the body has the function of reuptake of the mediator – when the substance returns from the synaptic cleft back into the presynaptic membrane of the axon and the action of the neurotransmitter stops. But sometimes reuptake is not enough, and more effective measures are needed – the destruction of the neurotransmitter molecule. These functions are also performed by proteins.

The COMT gene encodes the enzyme catechol‑O-methyltransferase, which destroys norepinephrine and dopamine. How well you will cope with stressful situations depends on the work of the protein. Owners of the active form of the COMT gene– warriors by nature – receive a reduced level of dopamine in the frontal lobe of the brain, which is responsible for processing information and pleasant sensations. Such people adapt better to stressful situations, they are open to communication, they have a better memory. But because of the low level of dopamine, they get less pleasure from life, are more prone to depression, and their motor functions are less developed. A low-activity variant of the COMT gene reverses the situation. The owners of the inactive mutation have good fine motor skills, are more creative, but they do not tolerate pain well, and once they get into a stressful situation, they plunge into irritability, impulsivity and anxiety. Also, mutations of the COMT gene are associated with Parkinson's disease and hypertension.

The gene of the enzyme monoamine oxidase A MAOA is responsible for the deactivation of monoamines – neurotransmitters with one amino group, which include adrenaline, norepinephrine, serotonin, melatonin, histamine, dopamine. The better the MAOA gene works, the faster the "clouding of the mind" caused by a stressful situation is neutralized and the faster a person is able to make informed decisions.

Sometimes even the MAOA gene is called the "criminal gene": certain mutations of the gene contribute to the emergence of pathological aggression. Due to the fact that the gene is located on the X chromosome, and girls have two copies of this gene, and boys have only one, there are statistically more "born criminals" among men.

Let's not blame everything on genetics – even with regard to the "furious" MAOA gene, everything is not easy: a study by New Zealand scientists has shown that the link between the gene and aggressive behavior manifests itself only in the presence of traumatic experience.

Understanding the principles of neurotransmitters allows you to take a fresh look at habitual emotions, mood changes, and even reconsider ideas about what actually shapes our personality. You can continue the fascinating process of self–discovery together with the Atlas genetic test - a great reason to find out your version of the DRD4, COMT and MAOA gene.

Continued: Adenosine, Acetylcholine, Glutamate and gamma-aminobutyric acid

Portal "Eternal youth" http://vechnayamolodost.ru  26.09.2016