How nighttime light led to depressed-like behavior in mice, the paper nature-neuroscience.

A paper published in nature neuroscience, a circadian rhathm gated subcortical pathway for nighttime light induced depressive like behaviors in mice, pointed out that mice exposed to blue light for two hours every night would have depression like behavior after a few weeks.the paper illustrates the neural pathways that cause this phenomenon, and may explain how excessive nocturnal light exposure affects humans.light affects a variety of physiological functions in mammals, including mood.although phototherapy during the day has antidepressant effects, excessive nighttime illumination from light pollution or electronic devices is considered to be associated with depressive symptoms.however, the neural mechanism behind this nocturnal light effect has not been elucidated.in this new study, Xue Tian of the University of science and technology of China, Zhao Huan of Hefei University of China and colleagues exposed mice to a two-hour dose of blue light every night for three weeks.the authors observed that depression like behavior was gradually developed in mice within three weeks (measured by the decrease of avoidance behavior and the decrease of sugar preference), and this behavior could continue for three weeks after the experiment.the authors propose a possible neural pathway to explain this result: a specific photoreceptor of the retina connects with the dorsal perihabenular nucleus and nucleus accumbens.blocking the connection between the two sites can prevent nocturnal light induced behavioral changes.the authors also found that the activation of this pathway by night light is much stronger than that by day light, which may explain why daytime light does not lead to behavioral changes.the mice exposed to blue light showed depressive behavior.| credit: Xue et al.