Sunlight exposure is known to affect mood, learning, and cognition. However, the molecular and cellular mechanisms remain elusive.

Researchers have shed new lights on the correlation between sunlight exposure and related neurobehaviors. Combining single-cell mass spectrometry isotopic labeling technique, the multi-institutional team uncovered a novel sunlight-activated glutamate biosynthetic pathway in the mouse brain. Such pathway may fundamentally contribute to our daily neurobehaviors such as mood, learning and cognition.

According to the senior author the ultraviolet (UV) light enhanced learning capacity has been observed in mice. "The mice without UV exposure typically require 6 rounds of training to adapt to the rotating rod," says the author, "however for the UV-exposed mice, they become smarter and only require 4 rounds of training."

The mechanism is examined using interdisciplinary techniques. It is revealed that the moderate UV exposure elevates the blood urocanic acid (UCA), which is later converted to glutamate (GLU) in the brain cells after crossing blood brain barrier. The synthesized GLU contributes to the enhanced learning capacity of mice. In addition to learning, such UV-triggered GLU synthesis could contribute to more sunlight-induced neurobehavioral changes such as memory and mood.

All UV-induced metabolic, electrophysiological, and behavioral effects could be reproduced by the intravenous injection of UCA and diminished by the application of inhibitor or short hairpin RNA (shRNA) against urocanase, an enzyme critical for the conversion of UCA to GLU.

http://en.ustc.edu.cn/news/201805/t20180523_316918.html

https://www.cell.com/cell/fulltext/S0092-8674(18)30507-5