In the Eye of the Beholder: Measuring and Standardising Light for Laboratory Mammals

Abstract

Light enables vision and exerts widespread effects on physiology and behaviour, including regulating circadian rhythms, sleep, hormone synthesis, affective state, and cognitive processes. Appropriate lighting in animal facilities may support welfare and ensure that animals enter experiments in a controlled physiological and behavioural state. Proper consideration of light during experimentation - both when it is explicitly employed as an independent variable and as a general feature of the environment - has the potential to provide more informative experimental designs and more reliable outcomes, contributing to Reduction and Refinement, helping to ensure more ethical animal use, and improving data quality. As such, it is unfortunate that ambient light for animals is typically quantified in units (lux) designed for human observers. We report the consensus views of an expert working group, with expertise spanning mammalian photobiology, neurobiology and animal husbandry and welfare, convened in February 2023 to agree upon metrics for light appropriate for non-human mammals and their application to improve animal welfare and the quality of animal research. We conclude that species-specific versions of the recently standardised a-opic metrology represent the best available approach to quantifying light. We provide methods for measuring these quantities; practical guidance for their implementation in husbandry and experimentation; and quantitative guidance on appropriate light exposure for laboratory mammals.

The transcription factor VAX1 in VIP neurons of the suprachiasmatic nucleus impacts circadian rhythm generation, depressive-like behavior, and the reproductive axis in a sex-specific manner in mice

“…Mice were maintained on a light/dark cycle of LD [12 h light, 12 h dark, average light intensity ~150-350 lux within the cage]. Based on the newly proposed light reporting method by ( 49 , 50 ), we determined the relative perception of light by mice using the mouse α-opics equivalent daylight illuminance (EDI, Supplementary Figure 1 ). We calculated that the α-opics for our experimental mice on LD to be melanopsin = 43.2 ± 16.9 lux, rod = 51.6 ± 19.8 lux, s-cone = 0.03 ± 0.01 lux, and m-cone = 57.1 ± 21.7 lux.…”