OXYTOCIN: STRUCTURE, PRODUCTION, MECHANISM OF ACTION, FUNCTIONS - NEUROPSYCHOLOGY - 2025

The oxytocin is a chemical that acts as a hormone in the body (mainly breast and uterus) and as a neurotransmitter in the brain. Its functions are related to some fundamental aspects of the reproductive system, such as sexual and emotional response, breastfeeding and childbirth.

Oxytocin is produced mainly in the hypothalamus, an area of ​​the brain closely related to emotional regulation. From there it passes into the bloodstream through the action of the pituitary gland once the neurons in the hypothalamus are activated for any reason.

Chemical structure of oxytocin. Glade.

The effects of oxytocin can be divided into two areas: those that are purely physical and those that are related to people's social behavior. Within the first group, we find the regulation of functions such as the contractions of the uterus during childbirth, or the production of milk in the mothers' breasts during lactation.

At the social level, oxytocin plays a fundamental role in aspects such as sexual arousal, affection and the formation of the romantic bond, trust, anxiety and attachment bonds. Because of this, it is popularly known as "the love hormone." However, it also seems to play an important role in the appearance of diseases such as anorexia, anxiety or addictions.

Structure of oxytocin

Oxytocin molecule. C ₄₃ H ₆₆ N ₁₂ O ₁₂ S _2. Source: MindZiper

Oxytocin is a peptide made up of nine amino acids, that is, a nonapeptide. Its sequence is as follows: cysteine ​​- tyrosine - isoleucine - glutamine - asparagine - cysteine ​​- proline - leucine - glycine (GYIQNCPLG). Cysteine ​​residues form a sulfide bridge.

The structure of oxytocin is very similar to that of another substance known as vasopressin. Both are nonapeptides with a sulfur bridge, and their sequence only differs by two amino acids.

Oxytocin has a molecular mass of 1007 daltons, and one international unit of this substance is equivalent to approximately 2 micrograms of pure peptide.

Production (where and how it is produced)

Oxytocin is produced within the hypothalamus, a brain structure that is primarily responsible for emotional regulation and the control of some unconscious impulses. Inside, those responsible for manufacturing this chemical are the magnocellular neurosecretory cells, which are located in the supraoptic and paraventricular nuclei.

From this point on, oxytocin is released into the bloodstream from the posterior lobe of the pituitary gland. Inside, this substance is packed in large vesicles with dense nuclei; and within them it is linked with a substance called neurophysin.

Oxytocin-neurophysin complex

Oxytocin made within the paraventricular nucleus of the hypothalamus goes directly to other parts of the brain and to the spinal cord, rather than going through the pituitary first and then being released into the bloodstream.

Hypothalamus

Neurosynthesis

Oxytocin is synthesized from an inactive precursor protein of the OXT gene. This protein also includes neurophysin I, which will later play the role of transporting oxytocin itself.

The neurosynthesis process occurs mainly when the protein is progressively hydrolyzed into small fragments, through the action of several different enzymes.

The last hydrolysis process is responsible for releasing the nonapeptide oxytocin, and its catalyst is peptidoglycine alpha-amidator monooxygenase (PAM). The function of this substance depends on vitamin C, so the level of this substance in the body will play an important role in the production of oxytocin.

Oxytocin is known to be metabolized by substances such as oxytokinase and leucyl / cystinyl aminopeptidase. Substances such as amastatin, bestatin, and leupeptin have also been found to inhibit the enzymatic degradation of oxytocin, although they also have similar effects on other peptides such as vasopressin.

Mechanism of action

As in the case of all hormones and neurotransmitters in our body, to cause its effect, oxytocin has to make links with a series of receptors sensitive to it. In the specific case of this hormone, the receptors are coupled to G proteins.

When oxytocin binds to one of its receptors, this causes calcium to be released from inside the cell it is in, which contracts a part known as the myometrium.

This effect plays a fundamental role, for example during childbirth, since it is considered that oxytocin is the main responsible for the presence of contractions in the female reproductive organ.

Functions of oxytocin

Oxytocin is one of the most important hormones in our body, and it fulfills a series of fundamental functions both physically, psychologically and emotionally. Next we will see what their main tasks are in each of these planes.

Physical effects

Most of the physical effects caused by oxytocin have to do with changes necessary to facilitate the birth of a child and its proper development. Therefore, these types of effects occur mainly in women, and are much more marked both during the time of birth and during later times.

On the one hand, oxytocin is one of the main substances responsible for causing contractions in the uterus during childbirth, in such a way that the necessary dilation occurs for the birth of the child. These contractions can also appear spontaneously during the weeks following delivery, as a way to clot the wounds left by the loss of the placenta.

On the other hand, oxytocin is also the main hormone responsible for regulating lactation. The mammary glands have a large number of receptors that bind to it, in such a way that milk production is stimulated during the first months or even years of the baby's life.

Psychological effects

On a psychological level, oxytocin is known as the "love hormone." This is due to the fact that it is one of the main responsible for the appearance of bonds of affection, among which are romantic or couple love, attachment between parents and children, and even friendship relationships, although to a lesser extent.

Thus, when we find ourselves in front of a person we value, we tend to secrete greater amounts of oxytocin. This process strengthens the emotional bond between both individuals, and fosters emotions such as trust or the desire to help the other.

The production of oxytocin becomes especially strong both during the birth of a child (which causes mothers to feel very attached to their babies) and during orgasm, especially the female one.

In this way, sex can provoke strong feelings of union between the people who practice it, in addition to the loss of desire for other people. This last effect has to do with the fact that oxytocin acts as a testosterone antagonist on sexual desire.

Oxytocin receptors

Oxytocin receptors are proteins that bind to this hormone and trigger its effects. They are normally known as OXTR receptors, since they are encoded in the gene of the same name, which in humans has been found on chromosome 3p25.

The OXTR protein is part of the G protein paired receptor family. Once it has formed a bond with an oxytocin molecule, it activates a series of secondary messenger channels that are responsible for causing the effects associated with this hormone throughout the organism.

Structure of the Ras protein, a monomeric G protein (Source: Mark 'AbsturZ' via Wikimedia Commons)

At the body level, oxytocin receptors can be found basically in two places: in the central nervous system, and in some organs related to the reproductive system.

In some mammals, in addition, receptors for this hormone have been found in organs such as the heart and kidneys. Thus, in humans the list of organs that contain receptors for oxytocin includes some such as the uterus, mammary glands, certain areas of the brain and the spinal cord.

Foods that stimulate its release

Oxytocin occurs naturally at many different times, but its levels can sometimes be below normal for a variety of reasons. If this happens, all kinds of problems can appear, such as a higher probability of suffering from anxiety or stress.

If you think your oxytocin levels may be too low, here is a list of foods that have been shown to stimulate its production.

Citrus

One of the most important elements in the production of oxytocin is vitamin C. For this reason, foods rich in this substance (such as oranges, lemons or mandarins) can have a very beneficial effect on people with levels very low of this hormone.

Avocado

The avocado is associated in a host of traditional cultures with sexual potency and well-being. Recent studies in this regard have discovered that this effect is due to the fact that it favors the production of oxytocin, a key component of sexual pleasure.

Spinach

Spinach has a multitude of beneficial effects on the body, among which are the reduction of systemic inflammation and the increase in the production of a multitude of substances, among which is oxytocin.

Coffee and green tea

Foods rich in caffeine and theine have been shown to have a significant effect on oxytocin production, especially in women.

References

1. "Oxytocin molecule" in: World of Molecules. Retrieved on: February 05, 2020 from World of Molecules: worldofmolecules.com.
2. "Oxytocin" in: You And Your Hormones. Retrieved on: February 05, 2020 from You And Your Hormones: yourhormones.info.
3. "What is the link between love and oxytocin?" in: Medical News Today. Retrieved on: February 05, 2020 from Medical News Today: medicalnewstoday.com.
4. "Oxytocin: Foods That Boost Your Love Hormone" in: Netmeds. Retrieved on: February 05, 2020 from Netmeds: netmeds.com.
5. "Oxytocin" in: Wikipedia. Retrieved on: February 05, 2020 from Wikipedia: en.wikipedia.org.