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Indolamines: what are they, types and characteristics

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What are neurotransmitters? They are the biomolecules that allow our neurons to exchange information and, ultimately, communicate. They enable an infinite number of processes at the cognitive level, such as thinking or decision-making.

There are different groups or families of neurotransmitters, as we will see below. One of them is the group of indolamines, neurotransmitters that contain an indole group; this group is made up of serotonin and melatonin.

In this article we will know its most relevant characteristics: location, effects and functions, agonist substances, etc.

  • Related article: "Types of neurotransmitters: functions and classification"

Indolamines: a type of neurotransmitter

We could say that neurotransmitters they are the messengers of the brain. But what do we mean by this?

What are the biomolecules that enable the exchange of information between the cells of the central nervous system (neurons). Thus, neurons communicate with each other through the synapse, a chemical process that is possible thanks to the action of neurotransmitters.

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There are different types of neurotransmitters in the brain. One of them is the one that includes Indolamines, a group or family of neurotransmitters that contain an indole group. At the chemical level, the indole group (also called benzopyrrole) is a heterocyclic organic compound, solid and colorless.

Its structure is bicyclic, and it is formed by a six-membered ring (benzene), which binds to another five-membered (pyrrole). Thus, indolamines constitute a family of brain neurotransmitters with the same molecular structure.

Classification of neurotransmitters

Before explaining in detail what indolamines consist of, let's see where they are located within the classification of the types of brain neurotransmitters that exist.

Within the neurotransmitters we find three large groups: amines, amino acids and neuropeptides. Indolamines, the neurotransmitters that we discuss in this article, are located within the group of amines, as we will see below.

1. Amines

The animas include two types of neurotransmitters: quaternary amines (such as acetylcholine) and monoamines. In turn, within the monoamines we find two more subgroups: catecholamines (which include dopamine, norepinephrine, and adrenaline) and indolamines (which include serotonin and melatonin).

2. Amino acids

The group of amino acid-type neurotransmitters includes the GABA (gamma-aminobutyric acid), glutamic acid (glutamate), glycine, and histamine.

3. Neuropeptides

Finally, we find the group of neuropeptides, which are small molecules made up of three or more amino acids. Within this group we find: enkephalins, endorphins, dinorphins and vasopressin.

Indolamines types

As we have seen, the group of indolamines includes two types of neurotransmitters: serotonin (5-HT or SA) and melatonin. We are going to know the most outstanding characteristics of each one of them.

1. Serotonin (5-HT)

The first of the indolamines that we are going to describe is serotonin; is it is synthesized from the transformation of an amino acid called tryptophan. That is, the precursor of serotonin is tryptophan, an essential amino acid necessary for our proper functioning, and which can be obtained from different foods.

  • You may be interested: "Serotonin: 6 effects of this hormone on your body and mind"

1.1. Location and functions

Serotonin is located in the nuclei of the Rafe, located in the brainstem of the brain; These, in turn, project to the cortex, hippocampus, and basal ganglia.

Regarding its functions, serotonin is heavily involved in regulating mood (like norepinephrine, another neurotransmitter), in reducing anxiety, in physiological processes such as sleep or appetite, in pain, etc.

In addition, it also inhibits aggressiveness and participates in erection in men (this appears when there are low levels of serotonin, or in the absence of it).

1.2. Agonist substances

All neurotransmitters, including indolamines, have agonist substances. Let us remember that agonist substances are those capable of exerting the same effects as others, binding to the specific cell receptor and causing the same action.

In the case of serotonin, its main agonist substances are: LSD, MDMA, fenfluramine and antidepressant drugs (except one of them, reboxetine, which is fourth generation and only acts on norepinephrine).

LSD (lysergic acid diethylamide) is a drug, also called lysergic or LSD 25, which belongs to the tryptamine family.

Is about a semi-synthetic psychedelic substance that acts on the central nervous system, and that is obtained from another substance, ergoline. Its psychological effects are diverse: perceptual alterations, sensitivity to details, distortions of reality, delusions, mental confusion ...

MDMA, also known as ecstasy, is another serotonin agonist. It is a drug that belongs to the amphetamine family. Its effects, like those of LSD, vary from person to person; some of them are: intense feeling of well-being, emotional warmth, increased extraversion, intensification in sensory perception, etc.

Another antagonist of indolamines (specifically serotonin) is fenfluramine. In this case, it is a drug used to treat obesity.

Finally, most antidepressant drugs are also antagonists of serotonin, since they increase its levels in the brain.

2. Melatonin

The melatonin it is another of the indolamines, along with serotonin. It is a hormone (or neurohormone) that is found in people but also in animals, plants, fungi, and bacteria. This is synthesized from tryptophan (just like serotonin). Specifically, s

Location and functions

Melatonin is mainly synthesized in the pineal gland, a fairly small endocrine gland, located in the brain (specifically, in the diencephalon).

Its production depends on the influence of another structure, the suprachiasmatic nucleus of the hypothalamus, that acts by receiving information from the retina, in relation to the daily patterns of light and darkness.

Regarding its functions, melatonin is heavily involved in sleep, enabling its start and maintenance. It also modulates circadian and seasonal rhythms.

As a highlight of this indolamine, the synthesis of melatonin is influenced by changes in ambient lighting. We usually synthesize more melatonin at night (when there is little light), and also at noon (at nap time). All of this makes sleep easier.

Bibliographic references:

  • Carlson, N.R. (2005). Physiology of behavior. Madrid: Pearson Education.
  • Pavlov, B. and Terentiev, A. (1970). Organic Chemistry Course. Translated by Victoria Valdéz Mendoza. Editorial MIR. Moscow.
  • Rosenzweig, M.R., Breedlove, S.M and Watson, N.V. (2005). Psychobiology: An Introduction to Behavioral, Cognitive, and Clinical Neuroscience. Barcelona: Ariel.
  • Sthal, S.M. (2002). Essential psychopharmacology. Neuroscientific bases and clinical applications. Barcelona: Ariel.
  • Sugden, D., Davidson, K., Hough, K.A. and Teh, M.T. (2004). Melatonin, melatonin receptors and melanophores: a moving story. Pigment Cell Res. 17(5): 454-60.
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