Nitric oxide (neurotransmitter): definition and functions

Some of you may think of nitric oxide as laughing gas, better known as “laughter gas”. Well, it’s nitrous oxide (N2O).

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

Since its discovery, nitric oxide has become one of the most studied molecules in human physiology. Studies confirm the natural ability of nitric oxide to prevent clotting, regulate inflammation, revitalize tissue, improve erectile dysfunction or kill invasive microorganisms and even eradicate cancer cells.

    In addition, nitric oxide promotes erection, and as a supplement is consumed in sports training and bodybuilding circuits, because it promotes resistance to fatigue and improves muscle development.

    Characteristics of nitric oxide

    And it is that this gas has aroused great scientific interest. As early as 1970, an American doctor named Ferid Murad realized that nitrates used when people suffer from chest pain or cardiovascular problems release nitric oxide. this substance has a dilating effect on the blood vessels and relaxes the muscle layer of 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 the functions of this are. 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 synthesis to occur, the presence of oxygen and a coenzyme (an organic molecule that binds to the enzyme) is required. reduced nad-phosphate (NADPH). In most living things, NO occurs in different types of cells.

    • Do you want to know the types of cells in the human body? You can do this by visiting our article: “Types of Main Cells in the Human Body”

    Functions in our body

    In addition to the studies I mentioned earlier that won the Nobel Prize for their authors, over the past three decades there have been over 60,000 studies on this gas.

    Nitric oxide performs different functions in the central and peripheral nervous systems, Which includes:

    • Reduces inflammation and blood clotting
    • Improves immune system performance by defending against bacteria and fighting cancer.
    • Increases recognition of the senses (for example, smell)
    • Increases endurance and strength and muscle development
    • It has a positive effect on gastric motility
    • Improves the quality of sleep
    • Improves memory

      Nitric oxide as a neurotransmitter

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

      However, this gas molecule works as a neurotransmitter and neuromodulator.

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

      1. It should be present in the presynapse
      2. It must be stored in the presynaptic terminal
      3. It should break free in the face of presynaptic nerve stimulation
      4. Exogenous administration of the substance would elicit a response identical to that elicited by presynaptic nerve stimulation and the drugs should cause the same changes in the response elicited by presynaptic nerve stimulation.
      5. At the synapse level, there must be mechanisms to stop the action of this neurotransmitter on the postsynaptic neuron.

      Since NO is a gas and its physicochemical functions are different from other neurotransmitters, it does not meet all of the above criteria. However, that does not mean that it does not act as a chemical messengerBut this type of transmission is a special form of transmission.

      In general, neurotransmitters are produced, stored and used when the nervous system needs them. Once these are used, an enzyme acts on them, often by breaking down. In the case of NO, this does not happen because it does not happen in advance. It is synthesized when it is needed.

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

      • Want to learn more about classic neurotransmitters? In our article “Types of neurotransmitters: functions and classification” we explain them.

      Nitric oxide and its relationship to Viagra

      Research on this gaseous compound has also led to the conclusion that nitric oxide is of prime importance in male erection. In fact, the drugs used to treat erectile dysfunction work on the nitric oxide pathway that allows blood to flow to the male organ.

      One of the most well-known drugs to treat this problem is sildenafil, which you probably know by its trade name: “Viagra”. But what is the relationship between Viagra and nitric oxide? Well, when we think we have an intimate relationship with someone or are in a situation where intimate stimulation is occurring, nitric oxide is released at the nerve endings of the male organ.

      This compound causes relaxation of the muscles, dilation of the cavernous bodies and blood vessels in this area, and this relaxation allows the entry of blood into the arteries and, consequently, the erection. When nitric oxide mobilizes towards the smooth muscle cells present in the blood vessels, it causes different chemical reactions by increasing the chemical messenger cGMP, this produces the dilation of the vessels which allows the circulation of the blood. Once cGMP has performed its function, it is degraded by the enzyme phosphodiesterase (PDE). Viagra blocks phosphodiesterase, preventing the breakdown of cGMP and improving erection.

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