Catecholamines: types and functions of these neurotransmitters

Dopamine, adrenaline and norepinephrine, 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 performed by each of these catecholamines, as well as the common characteristics between the three neurotransmitters.

    What are catecholamines?

    Catecholamines are a group of neurotransmitters from the class of monoamines, To which also belong tryptamines (serotonin and melatonin), histamine or phenethylamines. Dopamine, adrenaline and norepinephrine are the three main catecholamines.

    At the 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 get from foods high in protein 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 crucial in processes such as cognition, emotion, memory and learning, Motor control and regulation of the endocrine system. Norepinephrine and adrenaline play a key role in the stress response.

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

    The 3 main catecholamines

    Dopamine, epinephrine, and norepinephrine are chemically very similar, but each has distinctive features that require detailed description in order to understand the functions of each of these catecholamines.

    1. Dopamine

    Our body turns tyrosine into another amino acid, levodopa or L-DOPA, which in turn becomes dopamine. In turn, dopamine is the most basic catecholamine, and adrenaline and norepinephrine are both made from this neurotransmitter.

    When found in the brain, dopamine acts as a neurotransmitter; this means that it is involved in sending electrochemical signals between neurons. Instead, in the blood, it acts as a chemical messenger and helps vasodilate and inhibit the activity of the digestive system, immune system, and pancreas.

    The brain pathways in which dopamine is involved, mainly the black band and the mesolimbic, they relate to behavior motivated by reinforcement: Your levels increase when you get rewards. Thus, dopamine is important for processes such as learning, motor control and addiction to psychoactive substances.

    Alterations in these two neural pathways cause psychotic symptoms. Positive symptoms such as hallucinations have been linked to dysfunctions of the black streak pathway (which connects black substance to the striatum, a structure of the basal ganglia), and negative symptoms, such as emotional deficits, to dysfunctions of the brain. mesocortical.

    Destruction of dopaminergic neurons in the substantia nigra of the midbrain is the cause of Parkinson’s disease. This degenerative neurological disorder is characterized mainly by the presence of motor deficits and alterations, in particular tremors at rest.

      2. Adrenaline

      Adrenaline is generated by the oxidation and methylation of dopamine, Mainly in the locus coeruleus, located in the brainstem. The synthesis of this neurotransmitter is stimulated by the release of corticotropin in the sympathetic nervous system.

      Both adrenaline and norepinephrine, which we will talk about below, are considered stress hormones because when they act outside the nervous system, they don’t act like neurotransmitters but like hormones. They are linked to cardiac and respiratory regulation and to consumption of bodily resources to meet environmental challenges.

      Epinephrine and norepinephrine are essential for responding to multiple types of stressors and other activating processes in the body, such as exercise, exposure to heat, and lowered blood levels. oxygen or glucose.

        3. Noradrenaline

        The oxidation of adrenaline gives rise to norepinephrine, in the same way that dopamine converts it to adrenaline and tyrosine to dopamine. Like adrenaline, it acts as a neurotransmitter in the nervous system and a hormone in the rest of the body.

        Among the functions of noradrenaline we can highlight the cerebral alert, maintaining the waking state, the center 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 stores.

        Reduced levels of norepinephrine are associated with impairments in different types of learning, particularly the consolidation of long-term memory 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 the psychopathological level, this neurotransmitter is involved in stress and anxiety disorders, In major depression, Parkinson’s disease and Attention Deficit Hyperactivity Disorder.

        Bibliographical references:

        • Kobayashi, K. (2001). Role of catecholamine signaling in brain and nervous system functions: new knowledge from the molecular genetic study of mice. Journal of Investigative Dermatology Symposium Proceedings, 6 (1): 115-21.
        • Zouhal, H., Jacob, C., Delamarche, P. and Gratas-Delamarche, A. (2008). Catecholamines and the effects of exercise, training and sex. Sports Medicine, 38 (5): 401-23.

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