Neural Receptors: What They Are, Types And Functioning
The functioning of our nervous system houses extremely complex processes of transmission of nervous impulses and chemical substances, neurotransmission being the main phenomenon that allows neurotransmitters to travel throughout our nervous system, allowing everything from the correct 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.
Within the entire framework that enables the transmission of chemical substances 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 They are located in the cell membranes of the neuron
During neurotransmission, chemicals found in the intercellular space, such as neurotransmitters, encounter the cell membrane, along which neuronal receptors are located. 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 the molecular machinery that allows chemical communication between the 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 in both presynaptic cells and postsynaptic cells. In the first, the so-called autoreceptors are found which are intended to recapture the neurotransmitters released by that same cell, providing feedback and mediating the amount of neurotransmitters released.
However, when these are found in postsynaptic cells, the neuronal receptors receive signals that can trigger an electrical potential This regulates the activity of the ion channels. The influx of ions along open ion channels due to chemical neurotransmission can change the membrane potential of a neuron, resulting in a signal that travels along the axon and is transmitted between neurons and even to the entire neural network.
Is it the same as a sensory receptor?
The answer is no. While neuronal receptors are small agents found in the membranes of cells and whose mission is to transmit information through the reuptake of specific neurotransmitters sensory receptors refer to specialized nerve endings found in sensory organs.
Throughout our entire body (skin, eyes, tongue, ears, etc.) we find thousands of nerve endings whose main mission is to receive stimuli from the outside and transport this information to the rest of the nervous system, thus causing all types of responses and bodily sensations.
Types of neuronal receptors according to form of action
There are two main types of neuroreceptors which can be classified according to their functioning. These are ionotropic receptors and metabotropic receptors.
1. Ionotropic receptors
By ionotropic receptors we understand 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 “ligand”.
The binding site of these ligands in the receptors is usually located in a different portion of the protein. The direct union between the receptor and the ligand causes the opening or closing that is characteristic of ion channels; compared to metabotropics that use the so-called second messengers.
The operation of ion channels It will also be different depending on the voltage, that is, they open or close depending on the membrane potential. 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 which is found inside the cell. That is, they carry out indirect chemical neurotransmission.
These receptors They are usually coupled to G proteins and, while ionic receptors can excite or inhibit a response, metabotropic receptors have neither inhibitory nor excitatory functions, but rather exert a broad 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 signaling cascade that releases calcium stored in cell reserves.
Types according to the neurotransmitter
In addition to the classification of neurotransmitters according to the way in which they transmit information, they can also be classified according to the neurotransmitter to which they are going to be coupled.
These are some of the main classes of neuronal receptors:
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 dopamine.
3. GABAergic
Associated with the GABA neuroreceptor, it 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 acetylcholine (ACh) receptors 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 a feeling of euphoria to sedation or analgesic effects.
7. Serotoninergic
They are serotonin (5-HT) receptors and there are at least 15 subtypes within this classification.
