Journal
GENERAL AND COMPARATIVE ENDOCRINOLOGY
Volume 197, Issue -, Pages 56-64Publisher
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.ygcen.2013.12.005
Keywords
Seasonality; Photoperiodism; Light pollution; Pelage; Immune function
Categories
Funding
- National Science Foundation [IOS-1118792]
- JSPS Postdoctoral Fellowships for Research Abroad
- Direct For Biological Sciences
- Division Of Integrative Organismal Systems [1118792] Funding Source: National Science Foundation
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Photoperiodic regulation of physiology, morphology, and behavior is crucial for many animals to survive seasonally variable conditions unfavorable for reproduction and survival. The photoperiodic response in mammals is mediated by nocturnal secretion of melatonin under the control of a circadian clock. However, artificial light at night caused by recent urbanization may disrupt the circadian clock, as well as the photoperiodic response by blunting melatonin secretion. Here we examined the effect of dim light at night (dLAN) (5 lux of light during the dark phase) on locomotor activity rhythms and short-day regulation of reproduction, body mass, pelage properties, and immune responses of male Siberian hamsters. Short-day animals reduced gonadal and body mass, decreased spermatid nuclei and sperm numbers, molted to a whiter pelage, and increased pelage density compared to long-day animals. However, animals that experienced short days with dLAN did not show these short-day responses. Moreover, short-day specific immune responses were altered in dLAN conditions. The nocturnal activity pattern was blunted in dLAN hamsters, consistent with the observation that dLAN changed expression of the circadian clock gene, Period1. In addition, we demonstrated that expression levels of genes implicated in the photoperiodic response, Mel-1a melatonin receptor, Eyes absent 3, thyroid stimulating hormone receptor, gonadotropin-releasing hormone, and gonadotropin-inhibitory hormone, were higher in dLAN animals than those in short-day animals. These results suggest that dLAN disturbs the circadian clock function and affects the molecular mechanisms of the photoperiodic response. (C) 2013 Elsevier Inc. All rights reserved.
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