Dim light at night () significantly increased depression-like behaviors in postpartum mice.
Pregnant mice exposed to dLAN showed reduced sugar preference and increased immobility, indicative of depression-like symptoms.
dLAN exposure was associated with decreased levels of brain serotonin (5-HT) and brain-derived neurotrophic factor (BDNF) during the postpartum period.
The amplitude of circadian rest-activity behaviors and nighttime activity levels were diminished in mice exposed to dLAN.
Disruptions in were linked to depression-like behaviors and lower levels of 5-HT.
dLAN exposure altered the expression of circadian genes, particularly Per1, in the hippocampus of postpartum mice.
Simplified
Growing evidence suggests that dim light at night () may disrupt and provoke symptoms of anxiety and depression. Due to the inconvenience of pregnancy and caring for infants, there is a high prevalence of dLAN exposure among pregnant and postpartum women. However, the role and circadian mechanism of dLAN on depression, and anxiety during the postpartum period remain unclear. Pregnant mice were housed in either a light-dark cycle (LD; 12 h of 200 lux:12 h of 0 lux) or a light-dLAN cycle (dLAN; 12 h of 200 lux:12 h of 5 lux) during the gestational and postpartum periods. Depression- and anxiety-related symptoms were assessed by the open field test, sucrose preference test, and forced swim test. Hippocampal transcript profiles were examined using multi-timepoint transcriptome analysis to assess the effects of dLAN exposure. Our findings showed that dLAN significantly increased depression-like behaviors, such as decreased sugar preference and increased immobility time, and decreased levels of brain serotonin (5-HT) and brain-derived neurotrophic factor (BDNF) during the postpartum period. In addition, dLAN reduced the amplitude of circadian rest-activity behaviors and nighttime activity levels, and these disruptions were significantly related to depression-like behaviors and low levels of 5-HT. Moreover, dLAN disrupted the expressions of hippocampal circadian genes particularly Per1 in postpartum mice. These findings reveal that dLAN induces depression-like behaviors in postpartum mice, with disruptions in circadian rest-activity rhythms and rhythmic gene expression likely mediating the adverse effects of dLAN on these behaviors.
Key numbers
2.614
Decrease in sucrose preference
Sucrose preference percentage between control and groups mice on PPD10-12.
2.852
Increase in immobility time
Immobile time (s) during FST between control and groups mice on PPD14.
3.848
Lower serotonin concentration
5-HT concentration in the brain.
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Ethics approval and consent to participate: This study was solely focused on animal research. All animal procedures within this investigation were meticulously carried out in strict accordance with the relevant guidelines and regulations and approved by the Animal Care and Use Committee of Guangzhou Medical University (Approval No.GY2024-411). Competing interests: The authors declare no competing interests.
