Catecholamines: types and functions of these neurotransmitters.

One of the most important groups of neurotransmitters; includes the famous adrenaline.

Dopamine, adrenaline and noradrenaline, the three main catecholamines, are some of the most relevant neurotransmitters for our nervous system.are some of the most relevant neurotransmitters for our nervous system. In this article we will analyze the chemical properties and functions of each of these catecholamines, as well as the common characteristics among the three neurotransmitters.

What are catecholamines?

Catecholamines are a group of neurotransmitters of the monoamine class, to which the triamines also belong.to which also belong the tryptamines (serotonin and melatonin), histamine or phenethylamines. Dopamine, adrenaline and noradrenaline are the three main catecholamines.

At a chemical level these neurotransmitters are characterized by the presence of a catechol (an organic compound containing a benzene ring and two hydroxyl groups) and an amine in the side chain. They are derived from the amino acid tyrosine, which we obtain from protein-rich foods such as dairy products, bananas, avocados or nuts.

The main site of catecholamine synthesis is the chromaffin cells of the adrenal medulla, as well as the postganglionic fibers of the sympathetic nervous system. We will describe in more detail the characteristics of the synthesis of these neurotransmitters in the following sections.

The role of these neurotransmitters is fundamental in processes such as cognition processes such as cognition, emotion, memory, learning, motor control, motor controlThe role of these neurotransmitters is fundamental in processes such as cognition, emotion, memory and learning, motor control and regulation of the endocrine system. Noradrenaline and adrenaline are also key players in the stress response.

Increases in catecholamine levels are associated with increased heart rate and glucose levels and with activation of the parasympathetic nervous system. Catecholaminergic dysfunctions can lead to alterations in the nervous system, and consequently to neuropsychiatric disorders such as psychosis or Parkinson's disease.

The 3 main catecholamines

Dopamine, adrenaline and noradrenaline are very similar from a chemical point of view, but each of them has distinctive peculiarities that require a detailed description in order to understand the functions of each of these catecholamines. understand the functions of each of these catecholamines..

Dopamine

Our organism transforms tyrosine into another amino acid, levodopa or L-DOPA, which in turn is converted into dopamine. Dopamine, in turn, is the most basic catecholamine, and both adrenaline and noradrenaline are made from this neurotransmitter..

When found in the brain, dopamine plays a neurotransmitter role; this means that it participates in sending electrochemical signals between neurons. In the blood, on the other hand, it functions as a chemical messenger and contributes to vasodilation and inhibition of the activity of the digestive system, the immune system and the pancreas.

The brain pathways in which dopamine is involved, mainly nigrostriatal and mesolimbic, are related to reinforcement-motivated behavior.their levels increase when we obtain rewards. Thus dopamine is important for processes such as learning, motor control and addictions to psychoactive substances.

Alterations in these two neural pathways cause psychotic symptoms. Positive symptoms such as hallucinations have been related to dysfunctions in the nigrostriatal pathway (which connects the substantia nigra with the striatum, a structure of the basal ganglia), and negative symptoms, such as emotional deficits, to dysfunctions in the mesocortical pathway.

The destruction of dopaminergic neurons in the substantia nigra of the midbrain is the cause of Park's disease. is the cause of Parkinson's disease. This degenerative neurological disorder is characterized mainly by the presence of motor deficits and disturbances, in particular resting tremors.

2. Adrenaline

Adrenaline is generated from the oxidation and methylation of dopamine, mainly in the locus coerulea.mainly in the locus coeruleus, located in the brain stem. The synthesis of this neurotransmitter is stimulated by the release of adrenocorticotropic hormone in the sympathetic nervous system.

Adrenaline and noradrenaline, which we will discuss below, are considered the stress hormones, since when they act outside the nervous system they do not act as neurotransmitters but as hormones. They are related to cardiac and respiratory regulation and to the consumption of bodily resources to make consumption of bodily resources to cope with environmental challenges..

Both adrenaline and noradrenaline are essential in the response to multiple types of stressors and other processes related to the activation of the organism, such as physical exercise, exposure to heat and reduction of blood levels of oxygen or glucose.

3. Noradrenaline

The oxidation of adrenaline gives rise to noradrenaline, just as the oxidation of dopamine converts dopamine to adrenaline and tyrosine to dopamine. Like adrenaline, it plays the role of a neurotransmitter in the nervous system and that of a hormone in the rest of the body.

Among the functions of noradrenaline we can highlight brain alertness, the maintenance of wakefulness, the focus of attention, the formation of memoriesThe formation of memories and the appearance of feelings of anxiety, as well as the increase in Blood Pressure and the release of glucose reserves.

Reduced noradrenaline levels are associated with alterations in different types of learning, particularly the consolidation of long-term memories and latent learning. This function is probably due to the control of neuronal activity by noradrenaline in brain regions involved in learning, such as the amygdala.

At the psychopathological level, this neurotransmitter is involved in stress and anxiety disorders. is implicated in stress and anxiety disorders, in major depressionIt is also involved in major depression, Parkinson's disease and attention deficit hyperactivity disorder.