Nighttime dim light exposure alters the responses of the circadian system

Exposure to dim light at night (20 lux) is associated with a decrease in the amplitude of circadian rhythm in mice compared to standard light/dark conditions.

• Increased expression of the PER1 gene was observed at the trough of its rhythm in mice exposed to dim light.
• Light exposure at night reduced the expression of clock genes mPer1 and mPer2 in the brain's suprachiasmatic nucleus for the dim light group.
• Mice in dim light conditions showed increased activity during the daytime compared to those in standard light/dark conditions.
• After being placed in constant darkness, mice exposed to dim light exhibited shorter free-running periods.
• The phase shifting response to light exposure was smaller in the dim light group, indicating altered circadian function.

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