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Glutamate: the excitatory neurotransmitter par excellence

Glutamate is the main excitatory neurotransmitter of the central nervous system , released both by neurons and by the cells of the glia. The glutamatergic pathways are strongly involved in neuronal plasticity, in memory and learning and other complex functions.

Its receptor system is very complex, there are two different types that differ in their mechanism of action . On the one hand, fast receptors, called ionotropics, whose mechanism is based on ion channels. On the other hand, metabotropic receptors, whose mechanism uses G proteins.

It is suspected that alterations in this system are responsible for some neurodegenerative and neurotoxic disorders. In addition to being the main neurotransmitter in the brain, glutamate is also involved in the sense of taste, in the maintenance of intestinal cells and in the metabolism of liver cells.

Glutamate and taste: the umami taste

Glutamate: the excitatory neurotransmitter par excellence

The receptors for the different flavors reside in the taste buds of the tongue. Until relatively recently, the basic flavors were sweet, salty, bitter and acid. However, a fifth flavor associated with glutamate has recently been described: the umami taste. Originally, this name was given to the characteristic flavor of the broth, which could not be associated with any of the others.

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Monosodium glutamate

Monosodium glutamate is a salt derived from glutamate. This is used as an additive in many foods in order to give them a tastier and more pleasant taste. It is a substance surrounded by controversy and subject to constant evaluations. This is due to its addictive nature, which is why its use in foods is limited.

Glutamate as a neurotransmitter

What does it mean that it is “exciter”?

Glutamate: the excitatory neurotransmitter par excellence

Its role as exciter of the nervous system refers to its role as ” switch ” of the different routes . Thus, the cells that synthesize and release it are associated with other neuronal pathways with different functions. When the glutamatergic neuron releases its neurotransmitter, it sends an ignition signal to the associated pathways. In this way, the path is activated before this signal and the electric impulse is transmitted between them.

Glutamate plays the antagonistic role to GABA, the main inhibitor of the central nervous system. This behaves identically, but acting as a switch for shutting off the tracks.

For a correct functioning of the central nervous system it is necessary that there is a balance between inhibition and excitation. This balance translates a balance between GABA and glutamate.

Visit this article: Gamma-aminobutyric acid (GABA)

The glutamate receptors

Glutamate receptors are molecules to which neurotransmitter molecules bind specifically. This correspondence is similar to that of a key and its padlock. In this way, only glutamate molecules and those structurally similar can bind to them.

Once the union is produced , a series of processes are triggered inside the cell. The final result is the production and transmission of the electrical impulse from one neuron to another. Based on these processes triggered inside the cell, we speak of two different types of receptor:

  • Receptors associated with ion channels . When these receptors bind glutamate, they open a gate, which allows the passage of certain ions. The ionic flux modifies the electrical charge of the cell. This change is responsible for the transmission of the electrical impulse from one neuron to another.
  • Receptors associated with G proteins . In these cases, when the glutamate molecule binds to its receptor, a complex set of activation and deactivation of molecules within the cells is triggered. The final result of this biochemical cascade of reactions allows the transmission of the electrical impulse.

Toxicity

Glutamate: the excitatory neurotransmitter par excellence

It has been proven that an excessive release of glutamate is related to the death of neurons. In addition, studies have shown that by blocking different glutamate pathways with drugs, some neurological diseases seem to improve. Some of these pathologies with which the glutamate toxicity has been related are:

This opens a very important way of research when it comes to addressing certain pathologies. The latest evidence points to the development of new neuroprotective drugs.

Bibliography

  1. Albarracín SL, Balderón ME, Sangronis E, Cucufate A, Reyes FGR. L – glutamate: a key amino acid for sensory and metabolic functions. SciElo (Internet). Available at:
  1. Zarate beas C. Glutamate: from brain nutrient to neurotoxic. Science Magazine 2005 . 25-30.
  1. Köles L, Kató E, Hanuska A, Zádori ZS, Rubini P, Illes P. Modulation of excitatory neurotransmission by neuronal / glial signaling molecules: interplay between purinergic and glutamatergic systems. PubMed (Internet): Available at:

Glutamate: the excitatory neurotransmitter par excellence

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