Light affects behavioral despair involving the clock gene Period 1

Area of Science:

• Neuroscience
• Chronobiology
• Molecular Biology

Background:

• Light at night significantly impacts mammalian physiology and behavior, influencing mood and circadian clock resetting.
• The suprachiasmatic nuclei (SCN) play a key role in aligning biological timing with environmental light-dark cycles.

Purpose of the Study:

• To investigate the role of light at night in modulating mood-related behaviors in mice.
• To identify the specific brain regions and molecular mechanisms involved in light's effects on mood.

Main Methods:

• Mice were exposed to light at specific zeitgeber times (ZT 22).
• Genetic manipulation involved complete Per1 deletion and specific deletion in the lateral habenula (LHb).
• Mood-related behaviors were assessed, and gene expression in the mesolimbic dopaminergic system was analyzed using RNA sequencing.

Main Results:

• Light exposure at ZT 22 activated the clock gene Period1 (Per1) in the lateral habenula (LHb), affecting mood-related behaviors.
• Complete Per1 deletion resulted in depressive-like behavior and abolished the beneficial effects of light.
• Specific Per1 deletion in the LHb suppressed the beneficial effects of light on mood without altering baseline behavior.
• RNA sequencing revealed significant gene expression changes in the nucleus accumbens (NAc), particularly in sensory perception and G-protein coupled receptor signaling, which were dependent on Per1 induction.

Conclusions:

• Light at night influences mood-related behaviors in mice, partly through the induction of Per1 in the LHb.
• Per1 acts as a critical mediator, filtering light-induced gene expression changes in the mesolimbic dopaminergic system.
• These findings highlight a novel pathway linking light, circadian clock genes, and mood regulation.