What is noradrenaline for?

What is noradrenaline?

Noradrenaline is a neurotransmitter (chemical messenger of the brain) synthesized by certain neurons from an amino acid (constituting food proteins): tyrosine. It belongs to the family of catecholamines and acts as a hormone. It therefore influences different parts of the body and stimulates the central nervous system.

What is the difference between adrenaline and noradrenaline?

On the chemically, adrenaline and noradrenaline level are very close. However, noradrenaline only works thanks to alpha receptors while adrenaline can walk with alpha and beta receptors. Alpha receptors are only at the level of the arteries and beta are located in the heart, lungs, arteries and muscles. This explains why these two substances have slightly different functions. Noradrenalis is a precursor of adrenaline.

The effects of adrenaline (or epinephrine)

Adrenaline has powerful effects on the body, including:

• increased blood sugar;
• the elevation of the heart rate and the intensity with which the heart contracts;
• The relaxation of smooth respiratory tract muscles which improves breathing.

The purpose of these effects is to give additional energy to the body. In case of stress or fear, the body releases a flood of adrenaline to allow a quick response.

The effects of noradrenaline (or nor -reversing)

Noradrenaline increases:

• blood sugar;
• heart rate;
• The intensity with which the heart contracts.

The different roles of noradrenaline (in stress, fear, blood pressure …) are detailed later in this article.

How do we do a dosage of noradrenaline?

To assess noradrenaline levels dose in the blood, urine or cerebro-spinal liquid the amount of VMA (vanylmandelic acid) and MHPG (3-methoxy-4-hydroxyphenylglycol), degradation products of noradrenaline.

Who produces noradrenaline?

After his release, part of the noradrenaline is the subject of a reuptake by the neuron which issued it; Another part is degraded. One of the degradation products is 3-methoxy-4-hydroxyphenylglycol (MHPG), whose dosage in cerebrospinal fluid, blood or urine, gives an idea of ​​noradrenergic sensitivity.

Noradrenergic cellular bodies are concentrated in the brainstem, and in particular in the locus coeruleus. There are few noradrenergic neurons (40,000), but they project almost all of the brain, thanks to an impressive network of ramifications. Thus, a single neuron can give birth to 300,000 terminals in a region as distant as the cerebral cortex. Stimulation of the locus, or the direct application of noradrenaline has two effects on the neurons of a target region: it inhibits their basic activity, while increasing their reactivity to other stimuli. The “background noise” is reduced while the important signals are amplified.

At the peripheral level, noradrenaline is the neurotransmitter of the sympathetic nervous system. It is also a hormone released by the Medullosurrenal Glands.

What roles for noradrenaline?

Noradrenaline module attention, learning and facilitates the response to Reward signals : The greater the noradrenergic sensitivity, the more these features are amplified.

Noradrenaline, stress and fear

In the rat, the destruction of Locus Coeruleus leads to a total disappearance of fear. The interventions that increase sensitivity to noradrenaline in frontal regions prevent the animal from forgetting a behavior linked to a reward. They allow him to associate the memory of a avoided punishment more quickly with a particular activity. Conversely, Mary Schneider (University of Wisconsin) has shown that disrespectful monkeys are unable to integrate the group’s social behavior.

Any stressful stimulus increases noradrenaline levels, whether it is a simple argument or a traumatic event as a terrorist attack. This is because these stimuli require greater attention from us, in order to prevent their repetition. This phenomenon linked to noradrenaline is called “long -term potentiation” and it plays a very important role in the fear of fear. Thus, the effect of noradrenaline is so powerful that it is very difficult to get rid of an acquired fear. This is well with what is called post-traumatic stress syndrome.

These stressful stimuli which increases noradrenaline can also prove beneficial. For example, it has been shown that stress linked to learning a new instrument or exploring an unknown city increases the level of this neurotransmitter in the brain and promoting the connection between neurons.

Attention deficit, ADHD and noradrenaline

In humans, the decrease in noradrenaline affects the acquisition of new knowledge and associations. But caffeine, which increases the noradrenaline of the brain, improves the ability to accomplish repetitive, boring tasks, not sanctioned by rewards. The administration of tyrosine to depressive patients increases the secretion of noradrenaline. This treatment improves the hedonic component of their depression. Doctor Bruce Perry (Baylor College of Medicine, Houston, Texas) found that a reduced noradrenergic sensitivity in children is associated with “socially detached” behaviors. Doctor Perry believes that there is a correlation between a strong noradrenergic sensitivity and the search for “socially acceptable” sensations.

In children with attention deficit disorder with or without hyperactivity (ADHD), regular physical exercise seems to improve both symptoms and academic performance. However, physical exercise is one of the best ways to increase noradrenaline levels in the brain (read below). The drugs prescribed in the event of ADHD (such as methylphenidate contained in ritalin) increase noradrenaline and dopamine levels, another neurotransmitter. Another drug known to ADHD, atomoxetine (active molecule of the Stratera drug) only targets noradrenaline.

Noradrenaline and depression

The noradrenergic system continues beyond the locus coeruleus in the limbic system. At the latter level, a drop in noradrenergic activity could promote depression. Besides, certain depression drugs can act both on noradrenaline and serotonin: these are the IRSNA (mixed inhibitors serotonin and noradrenaline), such as Venlafaxine, Milnacipran and Duloxetine.

The action of noradrenaline on blood pressure

Noradrenaline is a neuromediator whose action was first characterized on the peripheral level, in particular for its cardiovascular effects on blood pressure and heart rate. Noradrenaline acts as a heart stimulant and promotes the Contraction of blood vessels, which increases blood pressure. It is thus urgently administered to people whose blood pressure drops dangerously.

How to increase noradrenaline?

Lack of noradrenaline, temperature shock and physical exercise

As we have seen, physical exercise represents a very good way to stimulate noradrenaline, which explains the improvement of memory and learning linked to sports. A study assessed the learning of a new language by students while they were doing stationary bicycle at the same time. The latter have better memorized and understood that the participants having remained without moving during learning.

Extreme temperatures also play the role of stimuli to increase noradrenaline levels and therefore attention and learning capacities. Studies on the practice of 80 ° C sauna or icy baths indicate that it raises the levels of this chemical messenger in the brain.

Food and noradrenaline

Like dopamine, noradrenaline is synthesized from two amino acids, the tyrosine and phenylalanine. These amino acids are found in protein -rich foods and in particular in turkey, duck, cheese cottage, oats, pork, eggs, chicken but also dark chocolate.