A new study found that melatonin and its metabolites promote the formation of long-term memories in mice and protect against cognitive decline, according to research at Tokyo Medical and Dental University.

The researchers familiarized mice with objects and gave them doses of melatonin and the 2 melabolites 1 hour later, followed by a test on their memory the next day. The team found that memory improved after treatment, and that N1-acetyl-5-methoxykynuramine, or AMK, was the most effective. All 3 accumulated in the hippocampal region of the brain, a region important for turning experiences into memories, according to the study authors.

Exposure to an object 3 times in a day was enough for young mice to remember the next day on the novel object recognition task. In contrast, older mice behave as if both objects are new and unfamiliar, which is a sign of cognitive decline, according to the study. However, 1 dose of AMK 15 minutes after a single exposure to an object helped older mice remember the objects up to 4 days later, according to the study.

The researchers discovered that long-term memory formation could not be enhanced after blocking melatonin from being converted into AMK in the brain.

“We have shown that melatonin's metabolite AMK can facilitate memory formation in all ages of mice," said lead researcher Atsuhiko Hattori in a press release. "Its effect on older mice is particularly encouraging and we are hopeful that future studies will show similar effects in older people. If this happens, AMK therapy could eventually be used to reduce the severity of Mild Cognitive Impairment and its potential conversion to Alzheimer's disease."

Melatonin: finally, a supplement that actually boosts memory. EurekAlert! https://www.eurekalert.org/pub_releases/2020-12/tmad-mfa121020.php. Published December 10, 2020. Accessed December 15, 2020.