Catecholamines: Types And Functions Of These Neurotransmitters
Dopamine, adrenaline and noradrenaline, the three main catecholamines, 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 between the three neurotransmitters.
Catecholamines are a group of neurotransmitters from the monoamine class, to which tryptamines (serotonin and melatonin), histamine or phenethylamines also belong. Dopamine, adrenaline and norepinephrine 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 through 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, emotion, memory and learning, motor control and regulation of the endocrine system. Likewise, norepinephrine and adrenaline are key involved in the stress response.
Increases in catecholamine levels are associated with increased heart rate and glucose levels and activation of the parasympathetic nervous system. Catecholamine dysfunctions can cause alterations in the nervous system, and consequently neuropsychiatric disorders such as psychoses or Parkinson’s disease.
Dopamine, adrenaline and norepinephrine are very similar from a chemical point of view, but each of them has distinctive peculiarities that make a detailed description necessary for this reason. understand the functions of each of these catecholamines
1. Dopamine
Our body transforms tyrosine into another amino acid, levodopa or L-DOPA, and this in turn is converted into dopamine. In turn, dopamine is the most basic catecholamine, and both adrenaline and norepinephrine are made from this neurotransmitter
When found in the brain, dopamine plays the role of a neurotransmitter; This means that it participates in sending electrochemical signals between neurons. On the other hand, in the blood it functions as a chemical messenger and contributes to vasodilation and inhibition of the activity of the digestive, immune and pancreas systems.
The brain pathways in which dopamine is involved, mainly the nigrostriatal and mesolimbic, are related to behavior motivated by reinforcement – Your levels increase when we get rewards. In this way, 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 linked to dysfunctions in the nigrostriatal pathway (which connects the substantia nigra to the striatum, a structure of the basal ganglia), and negative symptoms, such as emotional deficits, to dysfunctions in the mesocortical pathway.
Destruction of dopaminergic neurons in the substantia nigra of the midbrain is the cause of Parkinson’s disease This degenerative neurological disorder is characterized above all by the presence of motor deficits and alterations, particularly resting tremors.
Adrenaline is generated from the oxidation and methylation of dopamine, 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 norepinephrine, which we will talk about next, are considered stress hormones, since when they act outside the nervous system they do not do so as neurotransmitters but as hormones. They are related to cardiac and respiratory regulation and with the consumption of bodily resources to cope with environmental challenges
Both adrenaline and norepinephrine are essential in the response to multiple types of stressors and other processes related to the activation of the body, such as physical exercise, exposure to heat and the reduction of blood oxygen or glucose levels.
3. Norepinephrine
The oxidation of adrenaline gives rise to norepinephrine, in the same way that the oxidation of dopamine converts this to adrenaline and that of tyrosine to dopamine. Like adrenaline, it plays the role of a neurotransmitter in the nervous system and a hormone in the rest of the body.
Among the functions of norepinephrine we can highlight cerebral alertness, maintenance of the state of wakefulness, focusing of attention the formation of memories and the appearance of feelings of anxiety, as well as the increase in blood pressure and the release of glucose reserves.
Reduction in norepinephrine levels is 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 norepinephrine in brain regions involved in learning, such as the amygdala.
At a psychopathological level, this neurotransmitter It is involved in stress and anxiety disorders in major depression, in Parkinson’s disease and in attention deficit hyperactivity disorder.
