Removing Short Wavelengths From Polychromatic White Light Attenuates Circadian Phase Resetting in Rats

Abstract

Visible light is the principal stimulus for resetting the mammalian central circadian pacemaker. Circadian phase resetting is most sensitive to short-wavelength (blue) visible light. We examined the effects of removing short-wavelengths < 500 nm from polychromatic white light using optical filters on circadian phase resetting in rats. Under high irradiance conditions, both long- (7 h) and short- (1 h) duration short-wavelength filtered (< 500 nm) light exposure attenuated phase-delay shifts in locomotor activity rhythms by (∼40–50%) as compared to unfiltered light exposure. However, there was no attenuation in phase resetting under low irradiance conditions. Additionally, the reduction in phase-delay shifts corresponded to regionally specific attenuation in molecular markers of pacemaker activation in response to light exposure, including c-FOS, Per1 and Per2. These results demonstrate that removing short-wavelengths from polychromatic white light can attenuate circadian phase resetting in an irradiance dependent manner. These results have important implications for designing and optimizing lighting interventions to enhance circadian adaptation.

Circadian Potency Spectrum with Extended Exposure to Polychromatic White LED Light under Workplace Conditions

“…The Circadian Potency spectral sensitivity for extended polychromatic light exposures that is largely confined to blue wavelengths explains the near complete restoration of melatonin levels in humans (Rahman et al, 2011; Gil-Lozano et al, 2016) and attenuation of circadian phase resetting in rats (Gladanac et al, 2019) when <500-nm dichroic cutoff filters are used to eliminate violet and blue, but not green, wavelengths in extended 12-h exposures to polychromatic white light. Similarly, the narrow Circadian Potency spectral sensitivity explains the findings of Souman et al (2018) of melatonin restoration in violet-enriched blue-depleted light.…”

Short Wavelengths Contribution to Light-induced Responses and Irradiance Coding in the Rat Dorsal Lateral Geniculate Nucleus – An In vivo Electrophysiological Approach

“…Taking into consideration different physiological functions played by these two structures, namely, image and non-image visual functions, this is not surprising. Moreover, similar changes in the light spectrum led to disruptive effects on circadian behaviour (Gladanac et al, 2019).…”

Neuronal Responses to Short Wavelength Light Deficiency in the Rat Subcortical Visual System

“…An alternative approach to study light influence on NIF functions in behavioral studies is with the use of filtered light. Due to melanopsin’s substantial contribution to all NIF functions the most widely used filters are cut off/bandwidth filters and amber lenses/goggles that remove short wavelengths from polychromatic/visible light ( Rahman et al, 2008 , 2017 ; Wren et al, 2014 ; Gladanac et al, 2019 ). Interestingly, these approaches of filtering have also been successfully exploited in minimizing disruptive effects of night time light exposure on circadian rhythms, quality of sleep and cognitive performance in humans ( Gringras et al, 2015 ; Ayaki et al, 2016 ; Ostrin et al, 2017 ; Mortazavi et al, 2018 ; Kazemi et al, 2019 ; Domagalik et al, 2020 ).…”