Relevance of Electrical Light on Circadian, Neuroendocrine, and Neurobehavioral Regulation in Laboratory Animal Facilities

Abstract

Light is a key extrinsic factor to be considered in operations and design of animal room facilities. Over the past four decades, many studies on typical laboratory animal populations have demonstrated impacts on neuroendocrine, neurobehavioral, and circadian physiology. These effects are regulated independently from the defined physiology for the visual system. The range of physiological responses that oscillate with the 24 hour rhythm of the day include sleep and wakefulness, body temperature, hormonal secretion, and a wide range of other physiological parameters. Melatonin has been the chief neuroendocrine hormone studied, but acute light-induced effects on corticosterone as well as other hormones have also been observed. Within the last two decades, a new photosensory system in the mammalian eye has been discovered. A small set of retinal ganglion cells, previously thought to function as a visual output neuron, have been shown to be directly photosensitive and act differently from the classic photoreceptors of the visual system. Understanding the effects of light on mammalian physiology and behavior must take into account how the classical visual photoreceptors and the newly discovered ipRGC photoreceptor systems interact. Scientists and facility managers need to appreciate lighting impacts on circadian, neuroendocrine, and neurobehavioral regulation in order to improve lighting of laboratory facilities to foster optimum health and well-being of animals.

Effects of Duodenal 5-Hydroxytryptophan Perfusion on Melatonin Synthesis in GI Tract of Sheep

“…For example, it improves the meat quality and quantity of cashmere goats [ 13 , 14 ], reduces somatic cell count and mastitis in dairy cattle to improve the quality of the milk [ 15 , 16 ]. Currently, in husbandry industrial, the methods used to regulation of MT levels in animals are primarily to alter the light/dark cycle of the environments [ 17 , 18 ], or by implantation [ 19 , 20 ], injection [ 21 ], and oral administration [ 22 ] of MT. As to the exogenous melatonin administration, several factors should be considered including its bioavailability, acting duration, economic benefit, and delivery methods [ 22 ].…”

Advocating for Generalizability: Accepting Inherent Variability in Translation of Animal Research Outcomes

“…Recent ILAR publications provide summary overviews of important extrinsic factors like the room light cycle (80); social and behavioral factors (81); and the animal microbiota (82), which is strongly influenced by rodent chow formulations and can also vary wildly by brand and nutritional composition. Drinking water provided to laboratory animals is rarely considered in the experimental design, but recent evidence indicates that water source, microbial and chemical contaminants, and purification methods can result in potential experimental variability (83).…”

Hepatitis A Virus Infection in Cynomolgus Monkeys Confounds the Safety Evaluation of a Drug Candidate

“…Determining whether effects observed were the direct result of exposure to the test compound, and whether they are reliably human relevant, sometimes requires expert knowledge of the strengths and limitations of the experimental model and of the test methods employed. Confounding factors may include pre-existing variability in the experimental model, 14,15 uncontrolled environmental influences, [16][17][18] procedural errors, 19 and occasionally, opportunistic or background subclinical infections in experimental models. 9,20,21 This report describes investigations that were prompted by unexpected observations in a toxicology study with a novel, orally-active, small molecule in clinical development for the treatment of a rare genetic disease.…”