DOPAMINERGIC NEURONS: CHARACTERISTICS, FUNCTIONS AND PATHWAYS - GEOGRAFÍA - 2025

The dopaminergic neurons are brain cells which are responsible for producing dopamine and transmit to other cells of the nervous system. These types of neurons participate in a wide variety of biological processes, mainly movement, motivation and intellectual function.

In this way, the degeneration of these brain cells can produce a wide variety of conditions, among which are schizophrenia and Parkinson's disease.

Main pathways of dopamine. Source: NIDA, Quasihuman / Public domain

Currently, the knowledge about the molecular mechanisms involved in the regulation of dopaminergic neuron death is scarce. However, these cells of the central nervous system are the subject of a great deal of research.

Characteristics of dopaminergic neurons

A dopaminergic neuron is, by definition, a cell of the nervous system that is responsible for both generating and transmitting and receiving a substance known as dopamine.

In this sense, the classification in which dopaminergic neurons are found does not respond to their morphology, the synapses they establish or their function, but to the neurotransmitter they release.

Main dopamine transport routes within a dopaminergic synapse. Source: Smedlib, Pancrat / Public domain

In this sense, depending on the substance released by the cells, neurons can be divided into different groups, such as dopaminergic, gabaergic, glutamatergic, cholinergic, noradrenergic, etc.

With regard to dopaminergic drugs, as the name suggests, the neurotransmitter released is dopamine, a substance belonging to the catecholamine family found within the brain and whose activity generates the activation of different brain regions.

What is dopamine?

In order to properly understand what the main characteristics of dopaminergic neurons are, it is necessary to focus on the properties of the substance they release, that is, dopamine.

Dopamine is a neurotransmitter that is produced in a wide variety of animals, both vertebrates and invertebrates. Chemically it constitutes a phenylethylamine, that is, a type of catecholamine that performs neurotransmission functions in the central nervous system.

Specifically, this substance is found in the intersynaptic space of the brain and acts by activating five types of cellular dopamine receptors: D1, D2, D3, D4 and D5.

These receptors are contained by dopaminergic neurons, so this type of cell is in charge of both transmitting and releasing dopamine, as well as recapturing the particles of these substances released by other neurons of the same class.

These types of neurons are found in multiple regions of the nervous system but are especially prevalent in the substantia nigra. Likewise, the hypothalamus is another brain structure with high amounts of dopaminergic neurons.

Features

Dopaminergic neurons have a wide variety of functions within the brain of living beings. In fact, these types of cells have been linked to very diverse and different brain activities.

Specifically, the four activities in which dopaminergic neurons play a more important role are: movement, cognition, regulation of prolactin, and motivation and pleasure.

Movement

Dopaminergic neurons are essential cells to develop all the movement processes of the body.

Through its receptors D1, D2, D3, D3, D4 and D5, dopamine decreases the influence of the indirect pathway and increases the actions of the direct pathway involving the basal ganglia of the brain.

In fact, insufficient generation of these cells in the basal ganglia tends to generate the typical Parkinsonian symptoms of Parkinson's disease. Likewise, several investigations have shown that physical dopaminergic activation is a crucial element in maintaining motor skills.

Cognition

Dopaminergic neurons are also involved in cognitive processes. Specifically, these activities are carried out by this type of cells located in the frontal lobes of the brain.

In these regions, the functioning of dopamine regulates the flow of information from other areas of the brain. Alterations in dopaminergic neurons in this region can cause cognitive impairment, especially deficits in attention, memory, and problem solving.

Likewise, a deficit of dopamine production in the prefrontal cortex of the brain seems to contribute to the development of attention deficit hyperactivity disorder (ADHD).

Regulation of prolactin secretion

Dopaminergic neurons also stand out for being the main neuroendocrine regulator of prolactin secretion from the anterior pituitary.

Specifically, the dopamine released by the dopaminergic cells of the hypothalamus is responsible for inhibiting prolactin secretion.

Motivation and pleasure

Finally, one of the main functions of dopaminergic neurons at the brain level lies in the generation of the sensations of pleasure and reward.

In this case, dopamine cells located in the ventral tagmental area and in regions such as the nucleus accumbens, the amygdala, the lateral septal area, the anterior olfactory nucleus or the neocortex participate.

Dopamine is involved in naturally rewarding experiences such as eating, sexual behavior, and addictive substances.

Dopaminergic pathways

As has been previously observed, dopaminergic neurons are distributed in different regions of the brain. Likewise, depending on the area of ​​the nervous system in which they are, they are responsible for carrying out some functions or others.

In this sense, four different dopaminergic pathways have been described in the brain. These are: the mesolimbic route, the mesocortical route, the nigrostriatal route and the tuberoinfundibular route.

The mesolimbic pathway is responsible for transmitting dopamine from the ventral tagmental area to the nucleus accumbens. It is located in the midbrain and is related to the sensations of rewards. Alterations in this pathway are associated with schizophrenia.

The mesocortical pathway is responsible for transmitting dopamine from the ventral tagmental area to the frontal cortex. It is involved in cognitive processes and alterations in this pathway are also related to schizophrenia.

For its part, the nigrostriatal pathway transmits dopamine from the substantia nigra to the striatum. Alterations in this dopaminergic pathway are associated with Parkinson's disease.

Finally, the tuberoinfundibular pathway transmits dopamine from the hypothalamus to the pituitary gland and is associated with hyperprolactinemia.

References

1. Bear, MF, Connors, B. i Paradiso, M. (2008) Neuroscience: exploring the brain (3rd edition) Barcelona: Wolters Kluwer.
2. Carlson, NR (2014) Physiology of behavior (11 edition) Madrid: Pearson Education.
3. Morgado Bernal, I. (Coordinator) (2005) Psychobiology: from genes to cognition and behavior. Barcelona: Ariel.
4. Morgado Bernal, I. (2007) Emotions and social intelligence: the keys to an alliance between feelings and reason. Barcelona: Ariel.