Neural receptors: what are they, types and function

The functioning of our nervous system harbors processes of transmission of nerve impulses and highly complex chemical substances, neurotransmission being the main phenomenon that allows the neurotransmitters travel throughout our nervous system allowing from the proper functioning of the organs to emotional regulation.

One of the main components involved in this neurotransmission are neuronal receptors or neuroreceptors. Throughout this article we will talk about its main characteristics and operation, as well as the different classifications and main types.

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What are neural receptors?

Within the entire framework that enables the transmission of the chemicals typical of neurotransmission processes, we find neuronal receptors or neuroreceptors. These small elements are protein complexes, that is, they are made up of proteins, and are located in the cell membranes of the neuron.

During neurotransmission, chemicals found in the intercellular space, such as neurotransmitters, meet the cell membrane, along which the receptors are neuronal. When a neurotransmitter encounters its corresponding receptor, they will bind and generate a series of changes inside the cell.

Therefore, a membrane receptor is an essential piece of molecular machinery that enables chemical communication between cells. It is necessary to specify that a neuronal receptor is a specific type of receptor that only binds exclusively with a series of neurotransmitters and not with other types of molecules.

We can find neuroreceptors both in presynaptic cells and in postsynaptic cells. In the first, are the so-called autoreceptors, which are intended to reuptake the neurotransmitters released by that same cell, providing feedback and mediating the amount of neurotransmitters released.

However, when these are found in postsynaptic cells, neuronal receptors receive signals that can trigger an electrical potential. This regulates the activity of ion channels. The influx of ions along the open ion channels due to chemical neurotransmission, can change the membrane potential of a neuron, resulting in a signal that travels along of the axon and it is transmitted between neurons and even to the entire neural network.

Is it equal to a sensory receptor?

The answer is no. While neural receptors are small agents that are found in cell membranes and whose mission is to transmit information by reuptake of specific neurotransmittersSensory receptors refer to specialized nerve endings found in the sensory organs.

Throughout our entire body (skin, eyes, tongue, ears, etc.) we find thousands of nerve endings whose main mission is to receive the stimuli from the outside and transport this information to the rest of the nervous system, thus causing all kinds of responses and sensations bodily

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Types of neuronal receptors according to mode of action

There are two main types of neuroreceptors which can be classified according to their function. These are the ionotropic receptors and the metabotropic receptors.

1. Ionotropic receptors

By ionotropic receptors we mean those receptors through which ions can pass. They are considered as a group of transmembrane channels that open or close in response to the binding of a chemical messenger, that is, a neurotransmitter, which is called a "ligand".

The binding site of these ligands on receptors is usually located on a different portion of the protein. The direct union between the receptor and the ligand, causes the opening or the closing that this characteristic of the ionic channels; compared to metabotropics using so-called second messengers.

The functioning of ion channels it will also be different depending on the voltage, that is, they open or close depending on the potential of the membrane. In the same way, there are ion channels that activate by stretching, which means that they perform one function or another depending on the mechanical deformation of the cell membrane.

2. Metabotropic receptors

In contrast to ionotropic receptors that transmit directly, metabotropic receptors they don't have channels, so they use a second messenger found inside the cell. That is, they carry out an indirect chemical neurotransmission.

These receptors are usually coupled to G proteins and, while ionic receptors can excite or inhibit a response, receptors Metabotropic drugs have neither inhibitory nor excitatory functions, but rather exert a wide group of functions.

Among the main functions of metabotropic receptors we find those of modulating the action of excitatory and inhibitory ion channels, as well as the activation of a cascade of signals that releases calcium stored in the cell's reserves.

Types according to neurotransmitter

In addition to the classification of neurotransmitters according to the way in which they transmit of the information, these can also be classified according to the neurotransmitter to which they are engage.

Here are some of the main classes of neural receptors:

1. Adrenergic

They are activated by the catecholamines adrenaline and norepinephrine.

2. Dopaminergic

They play an important role in the control of emotions as they are linked to the dopamine.

3. GABAergic

Associated with the neuroreceptor GABA, is essential in the action of some drugs such as benzodiazepines, some epileptics and barbiturates.

4. Glutamatergic

They can be divided into ionotropic N-methyl-daspartate (NMDA) receptors and non-NMDA receptors.

5. Cholinergic

They are recipients of the acetylcholine (ACh) and are subdivided into nicotinic (N1, N2) and muscarinic.

6. Opioid

They bind to both endogenous and exogenous opioid neurotransmitters and their activation can cause anything from euphoria to sedation or analgesic effects

7. Serotonergic

They are serotonin receptors (5-HT) and there are at least 15 subtypes within this classification.