Long wavelength light reduces the negative consequences of dim light at night

Dec 9, 2022Neurobiology of disease

Long-wavelength light lessens the harmful effects of dim light at night

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Circadian Biology on OpenScience ↗PubMed ↗DOI ↗

Abstract

Exposure to short-wavelength enriched lighting significantly disrupted activity rhythms and social behaviors in mice.

Dim light at night (DLaN) increased repetitive behaviors and reduced social interactions in contactin-associated protein-like 2 knock out (Cntnap2 KO) mice.
Wild-type mice showed strong responses to short-wavelength enriched lighting, including reduced locomotor activity and robust phase shifts.
Mice lacking melanopsin-expressing retinal cells were resistant to the effects of dim light, suggesting a specific pathway for light's impact.
Shifting DLaN to longer wavelengths lessened negative impacts on activity patterns and social behaviors in both Cntnap2 KO and wild-type mice.
Short-wavelength lighting induced cFos expression in specific brain regions, indicating potential mediators of the observed effects.

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Many patients with autism spectrum disorders (ASD) show disturbances in their sleep/wake cycles, and they may be particularly vulnerable to the impact of circadian disruptors. We have previously shown that a 2-weeks exposure to dim light at night (DLaN) disrupts diurnal rhythms, increases repetitive behaviors and reduces social interactions in contactin-associated protein-like 2 knock out (Cntnap2 KO) mice. The deleterious effects of DLaN may be mediated by intrinsically photosensitive retinal ganglion cells (ipRGCs) expressing the photopigment melanopsin, which is maximally sensitive to blue light (480 nm). In this study, the usage of a light-emitting diode array enabled us to shift the spectral properties of the DLaN while keeping the intensity of the illumination at 10 lx. First, we confirmed that the short-wavelength enriched lighting produced strong acute suppression of locomotor activity (masking), robust light-induced phase shifts, and cFos expression in the suprachiasmatic nucleus in wild-type (WT) mice, while the long-wavelength enriched lighting evoked much weaker responses. Opn4mice, lacking the melanopsin expressing ipRGCs, were resistant to DLaN effects. Importantly, shifting the DLaN stimulus to longer wavelengths mitigated the negative impact on the activity rhythms and 'autistic' behaviors (i.e. reciprocal social interactions, repetitive grooming) in the Cntnap2 KO as well as in WT mice. The short-, but not the long-wavelength enriched, DLaN triggered cFos expression in in the basolateral amygdala (BLA) as well as in the peri-habenula region raising that possibility that these cell populations may mediate the effects. Broadly, our findings are consistent with the recommendation that spectral properties of light at night should be considered to optimize health in neurotypical as well as vulnerable populations. DTA

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Long wavelength light reduces the negative consequences of dim light at night

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