Melatonin can be the way to curb memory loss – 08/31/2023 – Equilibrium

Melatonin, a hormone released by the body when it’s time to sleep, has been increasingly pointed out by science as an intensifier of the fixation of long-term memories. A study conducted in Japan, however, not only confirmed this quality, but also revealed part of how this process takes place, opening the way for future therapies.

The discovery is a breakthrough in the possibility of new treatments, especially related to forgetfulness caused by increasing age. The results were published in June in the journal NeuroReport by researchers at Sophia University in Tokyo, and are in the animal testing phase.

The article describes a molecular physiological process called phosphorylation, which involves modification of certain proteins in brain nerve cells and leads to the consolidation of recognition of something already seen. After using melatonin, the observed rats had alterations in the levels of phosphorylation of five key proteins in the formation of long-term memory, allowing the authors to detect memory-increasing mechanisms induced by the substance.

In a statement from the university, the main author of the study, Professor Atsuhiko Chiba, from the Department of Materials and Life Sciences at the Faculty of Science and Technology, said that the objective of the research was to explore signaling pathways of melatonin receptors.

The team, also composed by doctors Masahiro Sano, from the University of Tohoku, and Hikaru Iwashita, from the Medical University of Kansai, investigated the effects of three compounds linked to the substance in the formation of memory.

In addition to the sleep hormone itself, they also analyzed N1-acetyl-5-methoxyquinuramine (AMK), a biological compound resulting from melatonin metabolism, and ramelteon, a drug that binds to and activates the melatonin receptor.

The study was done with male mice only to avoid “any likely data variability resulting from the reproductive cycles that occur in female mammals.”

Testing the memory

The formation of long-term memory in the animals was evaluated through a series of experiments of recognition of objections by the rats, which for three days in a row were placed in an arena for 5 minutes daily.

On the fourth day, two identical objects were placed in the experiment space and the rats were allowed to explore them for 5 minutes, in what was called the “training phase”. On the following day, one of the two objects was replaced by a new one and the rats spent more time exploring the unknown than the already familiar, proving the fixation of the memory of those first items.

In the next step, the effects of the substances on the cerebral hippocampus, an area that is the learning and memory center of the mammalian brain, were analyzed. “Initial experiments clearly showed that administration of melatonin, ramelteon, or AMK at a dose of 1 mg/kg facilitated long-term memory formation,” the researchers stated.

Risks of self-medication

Pharmaceutical biochemist Rafael Appel Flores, researcher and scientific director at the company Dr. Fisiologia, holds a postdoctoral degree in neuroendocrinology from the University of São Paulo (USP) and views the recent Japanese discovery with optimism, but recalls that it is a preliminary phase.

“This opens doors to unraveling the role of melatonin, including in the treatment of those with memory loss and the elderly, but, as much as the model is very close to what happens in humans, we cannot complete, studies in people are needed to arrive at the same conclusions”, he says.

The expert also points out that melatonin is not the only memory agent, as there are other factors involved, such as sleeping or taking breaks in studies.

“Various research, including in humans, demonstrates, for example, that a good night’s sleep, with more than seven or eight hours, after studying or learning new knowledge, is essential to consolidate new memories”, he says.

The main function of melatonin is related to the regulation of circadian rhythms, which are the biological patterns of activity and rest that are repeated approximately every 24 hours. The production of this substance is carried out by the pineal gland, which is sensitive to light and synchronizes our internal biological clock.

“We, human beings, are diurnal, we use the period of light to carry out our main activities and the night to adjust certain biological processes, such as melatonin, which increases in the body when it is dark and decreases when there is exposure to light, playing a role crucial role in the control of sleep and wakefulness”, says the biochemist.

As this regulatory hormone is naturally produced by the body, melatonin should not be consumed on its own. When recommended to improve sleep, it usually works only for those who have a deficiency in their production, which makes a medical evaluation essential.