Catecholamines are nothing more than neurotransmitters, a concept that we will address later, these are known as aminohormones. The definition etymological Catecholamine can be explained as follows: They are a group of substances among which adrenaline, norepinephrine and dopamine can be mentioned, these substances are synthesized from the amino acid known as tyrosine, this is how it is composed of a catechol group and a group Not me.
In this sense, catecholamines (CA) or aminohormones can be said to be all those substances that contain in their structure a catechol group and a side chain with an amino group. They can function in our body as hormones or as neurotransmitters.
But what exactly is a neurotransmitter?
This definition can be considered as the key to understanding everything that has to do with catecholamine. In this sense, the neurotransmitter can be defined as a kind of neuromediator or message, said in a scientific way is a biomolecule that makes neurotransmission possible.
What is neurotransmission?
It is nothing more than the transmission of information from a neuron, that is, a cell of the nervous system that goes to another neuron, a muscle cell or a gland, all this is achieved through the synapse, which is the branch that separates them. Catecholamines exert a hormonal function as they are produced in the adrenal glands and also in nerve endings, so they are considered neurotransmitters.
The first of these is tyrosine, which is used as a source in catecholaminergic neurons (catecholamine producers). These have their origin mainly in the chromaffin cells of the adrenal medulla and in the postganglionic fibers of the sympathetic nervous system.
There are catecholamines: norepinephrine and dopamineThey act as neurotransmitters in the Central Nervous System and as hormones in the bloodstream. Catecholamines generally produce physiological changes that prepare the individual and the body for fighting and other physical activities.
Relationship with certain diseases
Studies have long shown that dysfunctions in the catecholaminergic pathways are due to bipolar disorders and schizophrenia. While in motor functions, dopamine is involved in Parkinson's disease.
This is how catecholamine is formed
Catecholamine biosynthesis is a highly regulated process. Long-term regulation usually involves the amount of regulatory enzymes. Regulates the amount of tyrosine hydroxylase, and the amount of dopamine? -Hydroxylase. Sometimes short-term changes are needed, and they are regulated by different mechanisms:
The enzyme that catalyzes the rate-limiting stage (tyrosine hydroxylase) it is inhibited by Dopa and dopamine, because they compete with biopterin for binding sites.
Regulation of tyrosine hydroxylase by phosphorylation. In each subunit there are serine residues (positions 8, 19, 31, 40) that are phosphorylated. Serine residues 19 and 40 cause a more significant increase in activity when they are phorylated. Residues 40 are phosphorylated primarily by protein kinase A, and 10 by CAM kinase II. Terminal depolarization increases tyrosine hydroxylase activity, as calcium enters which activates kinase enzymes.
Once the catecholamines have been synthesized, they are stored inside synaptic vesicles known as granular or dense nucleus vesicles. Inside the vesicles there are substances called chromogranins, calcium and ATP in high concentration (1000 mM). Catecholamines are complexing with chromogranins.
There is also dopamine? -Hydroxylase, which is why the synthesis of norepinephrine takes place inside the gallbladder, at least in part. The system by which catecholamines enter the vesicles is a proton antiport system. The necessary proton gradient is carried out by a proton-ATPase pumping protons into it, so the pH is approximately 5,5. This uptake system has broad substrate specificity. So they can compete with endogenous catecholamines.
Process to release catecholamines
There are various processes that are key to the release of catecholamines, first of all we have adrenergic receptors (norepinephrine and adrenaline): These two neurotransmitters have different effects, which is explained by the presence of different receptors, which in each type of cell are coupled to different transduction pathways.
In smooth muscle, it can cause contraction if? Receptors are activated, and relax if they act on? 2 receptors. In the blood vessels they produce vasoconstriction and vasorelaxation.
However, the reverse of the vessels, in the bronchi produces bronchodilation. While in the digestive tract it causes constriction and relaxation. As soon as the heart increases the heart rate and its intensity; increasing cardiac output.
Adrenergic receptors are structurally related, but they have different second messengers. Are receptors distinguished? Y ?; Epinephrine and norepinephrine are agonists for both receptors, but these have more agonists and antagonists. The receptor ? it can be? 1 or? 2. The? 1 can be A, B, or D.
These three differ in antagonists, location, structure, and effector mechanism (adenylate cyclase). In this case, what matters is that adenylate cyclase causes a different effect at each site in the body. The ? they can be 1, 2 or 3. They differ in antagonists, and characteristics. But all 3 stimulate adenylate cyclase.
Importance in the daily functioning of the human body
These neurotransmitters represent great importance in the actions of our body, since they exert multiple functions. They participate in both neural and endocrine mechanisms.
One of these influences is the one that they exert on the central nervous system that they control are movement, cognition, emotions, learning and memory. Regarding stress, catecholamines play a fundamental role in the responses to it, releasing these substances when experiencing physical or emotional stress.
In 1990 researchers determined that at the cell level, these substances modulate neuronal activity by opening or closing ion channels according to the receptors involved.
How is its presence determined?
Catecholamine levels can be determined by studying and testing blood and urine. In fact, catecholamines are bound to approximately 50% of proteins in the blood.
When failures or drops in catecholamine neurotransmission occur, certain neurological and neuropsychiatric disorders are generated. One of them is depression, which is associated with low levels of these substances, contrary to anxiety. On the other hand, dopamine seems to play an essential role in diseases such as Parkinson's and schizophrenia.
Finally, it is important to understand that catecholamine levels may depend on us if we assume a certain diet that has an appropriate amount of component that stimulates this neurotransmitter. There are foods with a high presence of phenylalanine such as red meat, eggs, fish, dairy, chickpeas, lentils, nuts, etc.
In aspartame, the sweetener most used in the food industry, represents more than 60% of the world market of these additives widely used in soft drinks and diet products, it is also found there. While tyrosine can be found in cheese.
How does it make us feel?
Both substances act as sympathomimetic hormones. This means that they simulate the effects of hyperactivity on the sympathetic nervous system.
In such a way that when these substances are released into the bloodstream, an increase in blood pressure, greater muscle contraction, and an increase in glucose levels are experienced. As well as acceleration of the heart rate and respiration. This explains why catecholamines are critical in priming fight-or-flight responses to stress.
Catecholamine release
For the release of catecholamines to occur, the necessary release of acetylcholine is required. This release can occur, for example, when we detect a hazard. Acetylcholine innervates the adrenal medulla and produces a series of cellular events.
When adrenaline rises, an increase in the so-called contractile force of the heart is generated. In addition, the frequency of the heartbeat increases. This causes an increase in the supply of oxygen. In the same way, they increase the respiratory rate. In addition, it has powerful bronchial relaxing effects.
Finally, it is important to be aware that it makes us react more quickly to stimuli and that we learn and remember better. However, high levels of these substances have been associated with anxiety problems. While low levels of dopamine seem to influence the appearance of disturbances in attention, learning difficulties and depression.