Indolamines: what they are and functions

Indoleamines are a type of neurotransmitters that act at chemical synapses. These endogenous substances mediate communication between neurons throughout the central and peripheral nervous system. They are necessary to boost and balance signals in the brain and to keep it functioning.

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

What are indolamines?

Indolamines are a group of neurotransmitters in the nervous system that are characterized by the union of indole groups with an amine group. Indole is a bicyclic heterocycle in which the benzene ring is fused to a pyrrole ring. These and other neurotransmitters are chemical groups that facilitate the transfer of signals through nerve endings.

Indole is a fundamental structure for a large number of alkaloids and chemical compounds of therapeutic interest. Tryptophan has an indolic nucleus in its structure, which makes it an essential molecule to promote the release of the neurotransmitter serotonin like melatonin (Sainsbury, 2001).

In pharmacology, we can find several drugs derived from indole, such as indomethacin and tenidap, which are used as anti-inflammatories. Tenidap is used, especially, in the treatment of rheumatoid arthritis and osteoarthritis (Montes, 2009). While indomethacin extends its benefits for the treatment of bursitis, tendonitis and as an analgesic (Kubota et al., 2008).

The variety of structures and physiological activities in which indole occurs is perhaps the main reason why the synthesis of its derivatives has been of great interest at a chemical and medicinal level. Regarding its production, the Fisher indole synthesis is one of the most widely used methods for the preparation of indolic derivatives (Robinson, B., 1963).

Indoleamines are a type of neurotransmitters that include an indole group.

Types of indolamines and functions

The indolamine group includes two types of neurotransmitters: serotonin (5-HT or SA) and melatonin. Let’s learn a little about them and their most notable functions.

Serotonin

It is formed by the hydroxylation and decarboxylation of tryptophan. It is secreted by nuclei found in the medial raphe of the brain stem and that project to many areas of the brain. serotonin acts as an inhibitor of pain pathways in the spinal cord and its effects on higher areas of the nervous system are supposed to help regulate the affective state (Portilla et al., 2006).

One of the functions that has been attributed to this indolamine is the regulation of moods. When their levels are low, they predispose people to suffer from mood and impulse control disorders. Instead, high levels may help promote more constructive social interactions by decreasing aggression and increasing dominance (Young & Leyton, 2002).

Serotonin also plays various roles in the human body, such as influencing learning, memory, happiness, and reward, as well as physiological processes such as regulating sleep, behavior, appetite, and regulating bowel movements ( Bakshi and Tadi, 2021).

Another important function that is related to this indolamine is coagulation.. Serotonin is carried by platelets and released upon activation. This induces constriction of injured blood vessels and enhances platelet aggregation to minimize blood loss (Duerschmied and Bode, 2009).

Melatonin

Melatonin is a hormone synthesized in several places in the body, including the pineal gland, skin, lymphocytes, and gastrointestinal tract. Its synthesis and secretion is controlled by light and dark conditions. Light decreases its production and darkness increases it (Singh and Jadhav, 2014).

This hormone is synthesized from the amino acid tryptophan, which is converted into serotonin, and this into melatonin, through the action of the enzymes serotonin-acetyl-transferase and hydroxyindole-Omethyltransferase.

The best known function of this indolamine is sleep promotion. Melatonin participates in the regulation of sleep and wake cycles through its interactions with the suprachiasmatic nucleus of the hypothalamus and the retina, promoting sleep and inhibiting signals that promote wakefulness.

Melatonin has not only been associated with sleep cycles, but also with the regulation of seasonal reproduction, body weight and energy balance (Barrenetxe et al., 2004). In addition, it has been found to influence neuroendocrine rhythms and body temperature cycles. It may even be involved in early fetal development, with direct effects on the placenta, glial and neuronal development (Tordjman et al., 2017).

Melatonin is an indolamine that facilitates sleep and inhibits signals that promote wakefulness.

The relationship between indolamines and well-being

Serotonin and melatonin are not minor indolamines, on the contrary, their secretion is directly related to our well-being:

They help us regulate moods. They induce sleep. We know that not sleeping has negative consequences for our lives. They regulate our sleep and wake cycles. They intervene in the regulation of our behavior and appetite. They are an essential component for our happiness.

In conclusion, The proper functioning of indoleamines and their chemical balance helps us to have a healthy life. To a large extent, thanks to them we can experience pleasant sensations and regulate our mood. If we really want to be happy, indolamines cannot be missing from the equation.

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