Moderate levels of UV-B exposure increases glutamate levels, leading to improved learning and memory in mice.
Many of us have felt depressed or low during the dark winter months and light or phototherapy is often used to treat mood disorders. However, the mechanisms behind sunlight and neurobiology have not been very clear.
A new study published in Cell, by Wei Xiong and his group from the University of Science and Technology of China (Hefei, China), sheds some light on how UV could lead to changes in the brain. Although it is known that high UV exposure can cause several skin diseases, moderate levels of UV exposure can have beneficial effects on health.
When the researchers administered mice with low doses of UV-B rays for 2 hours, which was equivalent to 30 minutes of sunlight exposure, they showed increased levels of a compound called urocanic acid. Urocanic acid crosses the blood–brain barrier into the neurons where it is converted in to glutamate – a potent neurotransmitter. The increased glutamate levels can then strengthen the circuits related to learning and memory.
To assess this, the researchers went ahead to see if the mice performed better in learning and memory tests after the UV-B exposure.
“The mice without UV exposure typically require six rounds of training to adapt to the rotating rod,” said Xiong, the team leader of the study, “however for the UV-exposed mice, they become smarter and only require four rounds of training.”
This is the first study that has discovered a new pathway linking sunlight and neurotransmitters; shedding light on how our brains and sunshine may be linked.