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Johns Hopkins Bloomberg School of Public HealthCAAT

Animal Welfare Enhancement Awards

2007 Award Recipient

Laboratory animal facility dark phase light contamination and circadian disruption in rodents

Robert T. Dauchy, Manager
Laboratory of Chrono-Neuroendocrine Oncology
Bassett Research Institute

Controlled lighting in animal rooms has long been a concern to biomedical researchers and animal care personnel alike. Diurnal lighting protocols impact significantly the chronobiologic nature and outcome of scientific investigations.  Unfortunately, adherence to such protocols is often overlooked, thereby leading to the improper care and use of laboratory animals and spurious experimental results.

Since the early 1990’s the Laboratory of Chrono-Neuroendocrine Oncology at Bassett Research Institute, directed by David E. Blask, Ph.D., M.D., has spearheaded studies examining the effects of light contamination at night. Studies from this laboratory have led to improvements internationally in both experimental protocols and animal facility design.

Here we examine the effects of different intensities of dark-phase light contamination in the animal facility on circadian rhythms in laboratory rats.  Animals will be monitored daily for metabolic, behavioral and physical changes.  Daily rhythms of melatonin, fatty acid, glucose, lactic acid levels will be investigated to determine the threshold intensity of dark-phase light exposure that causes disruption in normal physiology and metabolism.

From a human perspective, the risk of developing breast, prostate and colorectal cancers is significantly increased in industrialized nations, particularly in shift workers exposed to light at night. Western nations have increasingly become 24hr/day societies with greater numbers of people being exposed to light during the night at home and in the workplace.  Recent epidemiological studies and particularly experimental findings from the Bassett research group point to light at night-induced suppression of pineal melatonin productio