Today, a large part of the population knows that brain information is transmitted from bioelectric impulses that travel through beams of neurons or nerves to their destination, allowing this fact both the perception and the action of the internal and external environment.

Such transmission depends on the ability of the different neurons to establish a connection and transmit either voltage or neurotransmitters, requiring some kind of mechanism to detect and integrate these elements into the post-synaptic neuron to in turn generate a reaction in the form of action potential (or other types of potential). These elements are called receptors. There are mainly two main types of receptors, and the metabotropic receptors are one of the most important and well known .

Basic definition: what is a receiver?

The term recipient is often used in a wide range of contexts and fields, including physical, electronic or judicial. Another of these contexts is neuroscience, which is the one we focus on in this article.

At the neuron level, we call receptors the set of proteins that form part of the neuron membrane (or glial, as it has been shown that they also possess some receptors) and that act as a means of communication with the outside of the cell.

These are elements that act as a bridge or lock between the interior and exterior of the neuron, and that is activated only upon the arrival of certain substances (if they are controlled by neurotransmitters) or upon certain electrical charges in such a way that they open channels through which ions pass that will allow the generation of potentials of different types. They are especially important in the generation of excitatory and inhibitory potentials, which facilitate or inhibit the possibility of an action potential to appear, and which ultimately allow neuronal communication and information transmission.

There are different types of neurochemical receptors, the two main types being ionotropic and metabotropic receptors. It is on the latter that we will focus in this article.

Metabotropic receptors

Metabotropic receptors are among the main and most relevant types of neurochemical receptors, activated by reception with a specific ligand or neurotransmitter . These receptors are relatively slow acting, since their activation does not generate an immediate opening of the channel but rather triggers a series of processes that end up leading to it.

Firstly, it will be necessary for the neurotransmitter in question to bind to the receptor, which will generate the activation of the so-called G-protein, an element that can either open the channel so that certain ions can enter and/or leave or activate other elements, which will be known as second messengers. Thus, the action of these receptors is rather indirect.

Although metabotropic receptors are relatively slower than other types of receptors, the fact is that their performance is also more durable over time. Another advantage of these receptors is that allow the opening of several channels at the same time, since the second messengers can act in cascade (generating the activation of different proteins and substances) in such a way that the action of the metabotropic receptors can be more multitudinous and allow the generation of some type of potential more easily.

And not only do they make it possible to open channels: the second messengers can have different performances within the neuron, and can even interact with the nucleus without having to open a channel to do so.

Some neurotransmitters with metabotropic receptors

Metabotropic receptors are very common in our nervous system , interacting with different types of neurotransmitters. Below we will mention some more specific examples of the neurotransmitters that serve as a link to some of the metabotropic-type receptors present in our body.

1. Acetylcholine and muscarinic receptors

Acetylcholine is one of the substances that possess a specific type of metabotropic receptors, the so-called muscarinic receptors. This type of receptor can be both excitatory and inhibitory, generating different effects depending on its location and function.

This is the predominant type of cholinergic receptor in the central nervous system , as well as in the parasympathetic branch of the autonomic nervous system (linked to the heart, intestines and salivary glands).

However, it should be noted that acetylcholine also has other types of receptors, nicotines, which are not metabotropic but ionotopic.

2. Dopamine

Dopamine is another substance with metabotropic receptors. In fact, in this case we find that all the dopaminergic receptors are metabotropic , with different types depending on whether their action is excitatory or inhibitory and whether they act at a pre or post-synaptic level.

3. Noradrenaline and adrenaline

Like dopamine, from which it is derived, noradrenaline also has all its metabotropic channels. Adrenaline, derived from noradrenaline, does, too. They are found both inside and outside the nervous system (for example in fat tissue) and there are different types depending on whether they are excitatory or inhibitory or whether they act pre or post-synaptic .

4. Serotonin

Serotonin also has metabotropic receptors, this being the majority type. However, the 5-HT3 receptor is ionotropic. They are mostly of the inhibitory type.

5. Glutamate and the metabotropic receptor

Glutamate is one of the main excitatory substances in the brain , but most of its receptors (and the best known, such as NMDA and AMPA) are ionotropic. Only one type of glutamatergic receptor has been identified that is not, simply called the glutamate metabotropic receptor.

6. Gamma-aminobutyric acid or GABA

Unlike glutamate, GABA is the main brain inhibitor. Two basic types of receptors have been identified, GABAb being the metabotropic type.

Bibliographic references:

  • Gómez, M.; Espejo-Saavedra, J.M. and Taravillo, B. (2012). Psychobiology. Manual CEDE de Preparación PIR, 12. CEDE: Madrid.
  • Kandel, E.R.; Schwartz, J.H.; Jessell, T.M. (2001). Principles of Neuroscience. Madrid: McGrawHill.