We review the characteristics of this neurotransmitter so closely linked to emotions.
Brain substances are strongly involved in physiological processes of the organism, but also in psychological functions.
One of these substances, specifically a brain neurotransmitter, is serotonin , closely related to emotions.
On a psychological level, serotonin is related to mood, anxiety and depression , and on a physiological level, with sleep processes, blood coagulation, sexual function, etc. In this article we will learn about its characteristics, origin, uses, functions, receptors, and how it is related to antidepressants.
- Recommended article: “The 10 most important types of neurotransmitters (and their functions)”
Serotonin: what is it exactly?
Serotonin is a brain substance found in cells. It acts as a brain neurotransmitter, that is, it transmits information between neurons . Also called 5-hydroxytryptamine, or 5-HT for short.
This substance is synthesized from the conversion of tryptophan (a type of amino acid). Tryptophan is obtained from some foods; thus, serotonin in the brain is synthesized from essential amino acids (tryptophan) that we obtain from the diet.
Where is it located?
Serotonin is mainly found in the brain, but also in the intestines and in blood platelets. On the other hand, in addition to the body, serotonin is also found in other animals and plants.
At the brain level, serotonin is found especially in certain areas of the brain: specifically, where there is more serotonin is in the Rafe nuclei of the brainstem. These nuclei project to the cerebral cortex, the hippocampus and the basal ganglia, among other areas.
receivers
There are 9 different types of receptors for serotonin : 8 of them are metabotropic, and 1 of them is ionotropic (specifically 5-HT3, an inhibitory receptor involved in vomiting).
Relationship with antidepressants
This substance is related to well-being and happiness. However, in people with depression, the levels of serotonin (and other neurotransmitters, such as norepinephrine) are well below normal.
That is why antidepressants have proven to be effective for this type of patient, because they raise serotonin levels through different mechanisms of action (inhibiting its reuptake, for example) (everything will depend on the type of antidepressant used).
Functions
Serotonin is involved in various physiological processes such as: sleep, digestion, sexual function and appetite . On a psychological level, serotonin is related to social behavior, emotions, mood, memory, well-being and sexual desire or appetite.
Various studies have shown that low serotonin levels are linked to depressed mood and poor memory, among other effects. Let’s see some of the functions and processes in which serotonin is involved:
1. Sleep regulation
As we mentioned at the beginning, one of the functions of serotonin is to regulate sleep . This is so because it is a precursor of melatonin (a hormone that is involved in the sleep cycle and is also synthesized from tryptophan).
In this way, serotonin helps regulate circadian sleep-wake cycles, as well as the internal biological clock.
2. Mood regulation
Another widely known function of serotonin is its regulation of mood (norepinephrine also has this function).
That is why antidepressants, and also anxiolytics, act on it, increasing its levels. Thus, serotonin also has a regulatory function of anxiety and stress (decreasing its levels).
3. Inhibition of aggressiveness
Serotonin also inhibits aggressiveness, modulating the emotions associated with it . This has been studied in decision-making processes and has been confirmed. Thus, in various studies it has been observed how there is greater aggressiveness in people without previous aggressiveness, in whom a reduction in serotonin levels in the brain has been induced.
In this way, when we are fasting, we are more likely to feel aggressive, since serotonin is ultimately obtained from the diet (from essential amino acids).
4. Sexual function
On a sexual level, adequate levels of serotonin facilitate erection in men . These levels must be low or null, since an excess of serotonin produces the opposite effect, that is, the inhibition of the erection.
Thus, in general, serotonin is known to inhibit sexual function (also in women); This is also evidenced by the use of antidepressants such as SSRIs, which end up leading to problems of sexual dysfunction.
agonist substances
Agonist substances are those that bind to the same receptors as the substance for which they are agonists (in this case, serotonin), and cause a certain action in the cell ; This action is the same or similar to that produced by serotonin. That is, they are substances that “mimic” the effect of others, or that increase their concentration.
In the case of serotonin, there are the following agonists:
1. LSD
LSD is a type of drug that exerts effects on serotonin, enhancing its effects . Actually, its name is lysergic acid diethylamide, also called LSD-25.
It is a semi-synthetic psychedelic substance that produces various psychological and physical effects, such as: pupil dilation, sweating, insomnia, tremors, dry mouth, increased heart rate and body temperature, perceptual distortions (hearing and usually visual), hallucinations and “disconnection” with reality.
When LSD is taken, the first effects appear between 30 and 90 minutes after ingestion, and last between 7 and 12 hours.
2.MDMA
MDMA is another type of drug, also a serotonin agonist , since it generates a greater release of it (also norepinephrine and, to a lesser extent, dopamine).
Through the excessive release of serotonin produced by MDMA, the mood is stimulated, which can become excited or euphoric.
However, taking MDMA, like many other drugs, ends up being harmful, and people who use it regularly have been known to develop symptoms of depression, anxiety, paranoia, and confusion. In addition, they also present a deterioration in attention and memory.
3. Fenfluramine
Fenfluramine is an anorectic or anorexigenic drug, used in cases of obesity . Its main effect is appetite suppression. Structurally it resembles amphetamines (stimulants).
Although its mechanism of action is not really known exactly, it is related to the inhibition of serotonin reuptake. Thus, it is known that a decrease in serotonin causes hunger, and that its release, on the other hand, produces appetite suppression.
4. Antidepressant drugs
Antidepressants , whatever their type (tricyclics, SSRIs…) are serotonin agonists, and increase their concentration levels in the brain. All of them are, except one, reboxetine, a 4th generation antidepressant that only acts on norepinephrine.
Bibliographic references
- Carlson, N.R. (2005). Physiology of behavior. Madrid: Pearson Education.
- McIntosh, J. (2018). What is serotonin and what is its function? Medical NewsToday.
- NIDA. (2017). MDMA (ecstasy) abuse. Retrieved from https://www.drugabuse.gov/es/mdma-abuse-ecstasy in 2019, July 26.
- 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.