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Nitric oxide (neurotransmitter): definition and functions

Nitric oxide (neurotransmitter): definition and functions

June 6, 2023

Some of you certainly think that nitric oxide is a laughing gas, better known as "laughing gas". Well, that's nitrous oxide (N2O).

In this article we will talk about nitric oxide, also called nitrogen monoxide or NO (for its acronym in English), is a fat-soluble gas molecule that acts in the brain as a neurotransmitter and carries out different functions within our body.

Since its discovery, nitric oxide has become one of the most studied molecules in human physiology. The studies confirm the natural capacity of nitric oxide to prevent coagulation, regulate inflammation, revitalize tissues, improve erectile dysfunction or kill invading microorganisms and even eradicate cancer cells.

  • Related article: "Types of cancer: definition, risks and how they are classified"

In addition, nitric oxide favors the erection, and as a supplement it is consumed in the circuits of sports training and muscle building, since it favors resistance to fatigue and improves muscle development.

Characteristics of nitric oxide

And it is that this gas has aroused great scientific interest. Already in 1970, an American doctor, named Ferid Murad, noticed that nitrates that are used when people suffer chest pains or cardiovascular problems release nitric oxide, because This substance has a dilator effect for blood vessels and relaxes the muscular layer in the endothelium .

A few years later, in 1987, studies confirmed that the human body produces nitric oxide, which led to research on how it is formed, what it does and what are the functions of this compound in the human body. In 1998, the authors of these discoveries, Robert Furchgott, Ferid Murad and Louis J. Ignarro, received the Nobel Prize.

How nitric oxide is synthesized

Nitric oxide is synthesized from the protein amino acid arginine and L-citrulline , a non-protein amino acid, thanks to the action of an enzyme called nitric oxide synthase (NOS). In addition, for the synthesis to occur, the presence of oxygen and a coenzyme (an organic molecule that binds to the enzyme) is necessary. the reduced nad-phosphate (NADPH). In most beings, NO is produced in different types of cells.

  • Do you want to know the types of cells that exist in the human body? You can do it by visiting our post: "Types of major cells of the human body"

Functions in our organism

In addition to the studies that I mentioned before and that won the Nobel Prize for their authors, in the last three decades there are more than 60,000 investigations carried out on this gas.

Nitric oxide performs different functions in both the central and peripheral nervous systems , among which are:

  • Reduces inflammation and blood clotting
  • Improves the performance of the immune system by defending against bacteria and fighting cancer.
  • Increases the recognition of the senses (for example, smell)
  • Increase endurance and strength and muscle development
  • It has a positive effect on gastric motility
  • It enhances sleep quality
  • Improve memory
  • Related article: "Types of memory: how memory stores the human brain?"

Nitric oxide as a neurotransmitter

Neurotransmitters are chemical molecules that send signals within the nervous system. Nitric oxide, being a gas, does not fit with the classic definition of other neurotransmitters such as dopamine or serotonin.

But nevertheless, This gaseous molecule performs functions as neurotransmitter and neuromodulator .

According to the authors Fernández-Álvarez and Abudara Morales, neurotransmitters, classically, should meet these requirements:

  1. It should be present at the presinapsis
  2. It should be stored in the presynaptic terminal
  3. Should be released before presynaptic nerve stimulation
  4. Exogenous administration of the substance would elicit an identical response to that caused by presynaptic nerve stimulation and drugs should elicit the same modifications in the response caused by presynaptic nerve stimulation.
  5. In the synapse there must be mechanisms that allow the end of the action of said neurotransmitter substance on the postsynaptic neuron

Since the NO is one is a gas and its physico-chemical functions are different from other neurotransmitters, it does not fulfill all of the above criteria. But nevertheless, this does not mean that it does not act as a chemical messenger , but this type of transmission constitutes a particular form of transmission.

Generally, neurotransmitters are produced, stored and used when the nervous system requires them. Once they are used, an enzyme acts on them, often degrading them. In the case of NO this does not happen, because it does not occur in advance. It is synthesized at the time it is needed.

In addition, unlike other neurotransmitters, it does not have a localized effect, but diffuses in many directions and, being a gas, can affect many cells. Therefore, although both classical neurotransmitters and NO send information, they do so differently.

  • Would you like to know more about classic neurotransmitters? In our article "Types of neurotransmitters: functions and classification" we explain them to you.

Nitric oxide and its relation with Viagra

Research on this gaseous compound has also concluded that Nitric oxide is of utmost importance in male erection . In fact, the drugs used to treat erectile dysfunction act on the path of nitric oxide that allows the flow of blood to the male organ.

One of the best known medicines to treat this problem is Sildenafil, which you will probably know by its commercial name: "Viagra". But what is the relationship between Viagra and nitric oxide? Well, when we think about having intimate relationships with someone or we are in a situation where intimate stimulation occurs, Nitric oxide is released in the nerve endings of the male organ .

This compound causes the relaxation relaxation of the muscles, the dilation of the cavernous bodies and blood vessels in this area, and this relaxation allows blood to enter the arteries and, consequently, the erection. When nitric oxide is mobilized towards the smooth muscle cells present in the blood vessels, it causes different chemical reactions by increasing the cGMP chemical messenger, this produces the dilation of the vessels that allows the flow of blood. Once cGMP has performed its function, it is degraded by the enzyme phosphodiesterase (PDE). Viagra blocks phosphodiesterase, thus preventing the degradation of cGMP and improves erection.

Mechanism of Smooth Muscle Relaxation | Role of Nitric Oxide | IP3 Pathway (June 2023).

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