Definition

Noradrenaline is a neurotransmitter (chemical messenger of the brain) synthesised by certain nerve cells from an amino acid (food protein): tyrosine.

It belongs to the catecholamine family and acts like a hormone.

It therefore affects various parts of the body and stimulates the central nervous system.

What is the difference between epinephrine and norepinephrine?

Chemically, adrenaline and noradrenaline are very similar.

However, norepinephrine only works through alpha receptors, whereas adrenaline can work through both alpha and beta receptors.

Alpha receptors are only found in arteries, while beta receptors are found in the heart, lungs, arteries and muscles.

This explains why these two substances have slightly different functions.

The effects of noradrenaline

Noradrenaline increases:

• Blood sugar
• Heart rate
• The force with which the heart contracts

It can also constrict the blood vessels, raising blood pressure.

It is therefore given in an emergency to people whose blood pressure is falling dangerously.

What are the functions of norepinephrine?

Norepinephrine modulates attention, learning and facilitates response to reward signals: the greater the norepinephrine sensitivity, the more these features are enhanced.

Any stressful stimulus increases norepinephrine levels, whether it is a simple argument or a traumatic event such as a terrorist attack.

This is because these stimuli require us to pay more attention in order to prevent them from happening again.

This norepinephrine-related phenomenon is called "long-term potentiation" and plays a very important role in fear conditioning.

The effect of norepinephrine is so powerful that it is very difficult to get rid of an acquired fear.

A good example of this is post-traumatic stress disorder.

Those stressful stimuli that increase norepinephrine can also be beneficial.

For example, the stress associated with learning a new instrument or exploring an unfamiliar city has been shown to increase levels of this neurotransmitter in the brain and promote connections between neurons.

Conversely, a decrease in noradrenergic activity could promote depression.

In addition, certain antidepressants can act on both norepinephrine and serotonin: these are the SNRIs (serotonin and norepinephrine reuptake inhibitors), such as venlafaxine, milnacipran and duloxetine.

How to increase norepinephrine?

Exercise is a great way to stimulate noradrenaline, which explains the improved memory and learning associated with exercise.

One study looked at students learning a new language while riding an exercise bike.

They remembered and understood better than participants who remained motionless during the learning process.

Extreme temperatures also act as a stimulant to increase norepinephrine levels and thus attention and learning ability.

Studies of 80°C saunas and ice baths suggest that they increase levels of this chemical messenger in the brain.

Food and norepinephrine

Like dopamine, noradrenaline is synthesised from two amino acids, tyrosine and phenylalanine.

These amino acids are found in protein-rich foods, particularly turkey, duck, cottage cheese, oatmeal, pork, eggs, chicken and dark chocolate.