We explain what this neurotransmitter is and in which organic processes it is involved.
In this article we will talk about one of them: norepinephrine , a substance involved in the regulation of mood and in many other functions.
We will know what this substance consists of chemically, how it is altered in some mental disorders, its relationship with antidepressants , its characteristics, location, functions, receptors, agonists and antagonists.
- Recommended article: “The 10 most important types of neurotransmitters (and their functions)”
Norepinephrine: what is it?
Norepinephrine is a brain neurotransmitter, responsible for transmitting information between neurons.
Chemically, it is an amine (organic compound). The amines can be quaternary amines (such as acetylcholine [ACh]) or monoamines. In this case, norepinephrine is a monoamine . In turn, monoamines are divided into two groups: catecholamines and indolamines.
Norepinephrine belongs to the first group, along with dopamine and adrenaline. Catecholamines are substances that come from phenylalanine (an amino acid).
receivers
Norepinephrine receptors are of two types: presynaptic and postsynaptic . Specifically, we find α2 (alpha2), which can be pre- and postsynaptic, and α1, β1 (beta1) and β2, which are postsynaptic receptors.
Location
At the brain level, norepinephrine is a substance that is widely distributed throughout the brain ; however, there is an area of the brain where its concentration is especially high: the locus coeruleus , which is located in the pons, located in the brainstem.
On the other hand, a curious fact about norepinephrine is that it is a substance that acts as a brain neurotransmitter, but also as a hormone; when it acts as a hormone, it does so throughout the body. That is why its distribution covers the entire body.
Functions
Regarding its functions, norepinephrine participates in attentional processes (along with another neurotransmitter, dopamine ); It is also involved in the regulation of mood (like serotonin ), sleep and anxiety, appetite control, and sexual behavior. In addition, adequate levels of norepinephrine are related to the correct regulation of irritability.
On the other hand, it also intervenes in motivational processes, in the level of consciousness, alertness and wakefulness, and the perception of sensory impulses. Furthermore, norepinephrine is also involved in learning and memory; this can be related to people suffering from depression (with low levels of norepinephrine), since these patients frequently present alterations in these cognitive functions.
However, it should be noted that all of these functions are performed by norepinephrine in conjunction with some other neurotransmitter (with the exception of vigilance, which it is thought to perform alone). For example, the regulation of sleep and anxiety are related to the action of norepinephrine together with serotonin.
Abnormalities of norepinephrine in some disorders
Norepinephrine is a substance that can be altered in different mental disorders, as we will see below.
1. Depression
It has been observed how depressive patients present a deficit of this substance; That is why antidepressants, as we will see later, exert their effects on this substance, increasing its levels (along with serotonin and dopamine).
In this way, thanks to the studies and the results provided by antidepressants, norepinephrine deficits have been related to the aetiology of depression . Specifically, it was three researchers, Schildkraut, Bunney and Davis, who stated in 1965 that norepinephrine caused depression; They did it through a theory, considered the first attempt at a biological explanation for this disorder.
2. Eating behavior disorders (ED)
In addition, norepinephrine also presents alterations in people with an eating disorder ; These alterations translate into a decrease in its concentration.
This decrease has been related to some typical symptoms in these patients, such as bradycardia, hypothermia, depression and arterial hypotension ; that is, norepinephrine is believed to be responsible for them.
agonists
The norepinephrine agonist substances, that is, those that enhance its effect or increase its concentration or release , are mainly three.
1. Amphetamines
Amphetamines are drugs that stimulate the central nervous system (CNS) . Its action is linked to norepinephrine, but also to dopamine, serotonin and adrenaline. What amphetamines do is increase the presence of these substances in the brain. Regarding its relationship with norepinephrine, amphetamines inhibit its reuptake, causing this substance to be more free (and in greater quantity) in the synaptic space.
Amphetamines have a very high addictive potential; that means it is easy for people to become addicted to them. Its characteristic effect is an acceleration of brain functions. On the other hand, they accelerate heart rate, breathing and blood pressure.
As for negative effects, they can cause sweating, headaches, blurred vision, tremors and insomnia.
2. Cocaine
Cocaine is a norepinephrine, dopamine, and serotonin agonist drug . That is, it increases its concentrations in the brain. Specifically, what it does is block the reuptake of these monoamines at the monoaminergic terminals; this translates into an increase in the amount of these transmitters in the synapses.
These mechanisms are related to the euphoric properties of cocaine, especially in the case of serotonin and dopamine, and not so much with norepinephrine.
On the other hand, the increase in norepinephrine caused by cocaine, especially in the locus coeruleus, has been linked to increased blood pressure and vigilance.
3. Antidepressant drugs
Antidepressant drugs increase the concentration of norepinephrine in the brain ; that is why they are agonist substances of the same. It can be said that all antidepressants are norepinephrine agonists, except the SSRIs (Selective Serotonin Reuptake Inhibitors), which do not exert any action on this neurotransmitter (they only do so on serotonin).
Thus, examples of them would be: MAOIs (Monoamine Oxidase Inhibitors), tricyclic antidepressants, 4th generation antidepressants (reboxetine, venlafaxine…), etc.
Specifically, reboxetine is a selective norepinephrine reuptake inhibitor; Venlafaxine, meanwhile, is a dual inhibitor of serotonin (5-HT) and norepinephrine.
Antagonists
The antagonistic substances, on the other hand, exert just the opposite effect to the previous ones; thus, what they do is inhibit or block the effect (or release) of another substance (in this case, norepinephrine), or decrease its concentration. The norepinephrine antagonist is clonidine.
1. Clonidine
Clonidine is a drug prescribed as an antihypertensive . It exerts its action on the Central Nervous System (CNS), reducing its sympathetic efferents, as well as decreasing heart rate and blood pressure. Let us remember that the sympathetic system is related to the activation of the organism.
Bibliographic references
- Ambrose, E. (2008). Effects of cocaine in humans. Addictive Disorders, 10(3): 151-165.
- Castillero Mimenza, O. (2017). Norepinephrine (neurotransmitter): definition and functions. Psychology and Mind.
- Netter, F. (1989). Nervous system. Anatomy and physiology. Barcelona: Salvat.
- Robledo, P. (2008). amphetamines. Addictive Disorders, 10(3): 166-174.
- Stahl, SM (2002). Essential psychopharmacology. Neuroscientific bases and clinical applications. Barcelona: Ariel.
To the classic question “what do you do?” I always answer “basically I am a psychologist”. In fact, my academic training has revolved around the psychology of development, education and community, a field of study influenced my volunteer activities, as well as my first work experiences in personal services.