Dim light at night interacts with intermittent hypoxia to alter cognitive and affective responses

May 10, 2013American journal of physiology. Regulatory, integrative and comparative physiology

Dim light at night combined with low oxygen episodes changes thinking and mood responses

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Abstract

Exposure to dim light at night and intermittent hypoxia increased anxiety-like behaviors in mice.

Both dim light at night (dLAN) and intermittent hypoxia (IH) heightened anxiety-like behaviors in multiple assessments.
The combination of dLAN and IH resulted in increased depressive-like behaviors in the forced swim test.
IH led to impaired learning and memory performance in a passive avoidance task, though spatial working memory remained unaffected.
Dendritic morphology was negatively impacted, with decreases in cell body area and apical spine density in specific hippocampal regions.
Vascular endothelial growth factor (VEGF) expression was elevated by dLAN, while tumor necrosis factor-alpha (TNF-α) levels remained unchanged.

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Obstructive sleep apnea (OSA) and dim light at night (dLAN) have both been independently associated with alterations in mood and cognition. We aimed to determine whether dLAN would interact with intermittent hypoxia (IH), a condition characteristic of OSA, to alter the behavioral, cognitive, and affective responses. Adult male mice were housed in either standard lighting conditions (14:10-h light-dark cycle; 150 lux:0 lux) or dLAN (150 lux:5 lux). Mice were then exposed to IH (15 cycles/h, 8 h/day, FiO2 nadir of 5%) for 3 wk, then tested in assays of affective and cognitive responses; brains were collected for dendritic morphology and PCR analysis. Exposure to dLAN and IH increased anxiety-like behaviors, as assessed in the open field, elevated plus maze, and the light/dark box. dLAN and IH increased depressive-like behaviors in the forced swim test. IH impaired learning and memory performance in the passive avoidance task; however, no differences were observed in spatial working memory, as assessed by y-maze or object recognition. IH combined with dLAN decreased cell body area in the CA1 and CA3 regions of the hippocampus. Overall, IH decreased apical spine density in the CA3, whereas dLAN decreased spine density in the CA1 of the hippocampus. TNF-α gene expression was not altered by IH or lighting condition, whereas VEGF expression was increased by dLAN. The combination of IH and dLAN provokes negative effects on hippocampal dendritic morphology, affect, and cognition, suggesting that limiting nighttime exposure to light in combination with other established treatments may be of benefit to patients with OSA.

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Dim light at night interacts with intermittent hypoxia to alter cognitive and affective responses

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