Indolamines: what they are, types and characteristics


What are neurotransmitters? They are biomolecules that allow our neurons to exchange information and, ultimately, to communicate. They enable countless 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.

Indolamines: a type of neurotransmitter

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

What are the biomolecules that enable the exchange of information between 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.

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

Its structure is bicyclic, and is made up of a six-membered ring (benzene), which joins a five-membered ring (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 us see where they are within the classification of the types of brain neurotransmitters that exist.

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

1. Amines

The animas encompass 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 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, dynorphins and vasopressin.

Types of Indolamines

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; This 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 that can be obtained from different foods.

1.1. Location and functions

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


Regarding its functions, serotonin is highly involved in the regulation of mood (like norepinephrine, another neurotransmitter), in the reduction of anxiety, in physiological processes such as sleep or appetite, in pain, etc. .

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

1.2. Agonist substances

All neurotransmitters, including indolamines, have agonist substances. Remember that agonist substances are those capable of exerting the same effects as others, binding to the specific cellular receptor and causing its 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 family of tryptamines.

It is a semi-synthetic psychedelic substance that acts on the central nervous system, and 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 substance. 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 sensation of well-being, emotional warmth, increased extroversion, intensification of sensory perception, etc.

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

Finally, most antidepressant drugs are also serotonin antagonists, as they increase their levels in the brain.

2. Melatonin

Melatonin is another of the indolamins, 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 (like serotonin). Specifically, s

Location and functions

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

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

Regarding its functions, melatonin is strongly involved in sleep, making it possible to start and maintain it. It also modulates circadian and seasonal rhythms.

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

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