title: Dim light at night disrupts the short-day response in Siberian hamsters.
abstract: 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) (5lux 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.
authors.affiliation: Department of Neuroscience, The Ohio State University Wexner Medical Center, Columbus, OH 43210, USA. Electronic address: tomoko.ikeno@ousmc.edu.
authors.forename: Tomoko
authors.initials: T
authors.lastname: Ikeno
authors.affiliation: Department of Neuroscience, The Ohio State University Wexner Medical Center, Columbus, OH 43210, USA. Electronic address: zachary.weil@osumc.edu.
authors.forename: Zachary M
authors.initials: ZM
authors.lastname: Weil
authors.affiliation: Department of Neuroscience, The Ohio State University Wexner Medical Center, Columbus, OH 43210, USA. Electronic address: randy.nelson@osumc.edu.
authors.forename: Randy J
authors.initials: RJ
authors.lastname: Nelson
mesh_terms: D000818:Animals; D002940:Circadian Rhythm / Q000502:physiology* / Q000528:radiation effects; D005786:Gene Expression Regulation / Q000502:physiology / Q000528:radiation effects; D007987:Gonadotropin-Releasing Hormone / Q000235:genetics; D007028:Hypothalamic Hormones / Q000235:genetics; D007107:Immune System / Q000502:physiology* / Q000528:radiation effects; D008027:Light; D008070:Lipopolysaccharides / Q000494:pharmacology; D008297:Male; D009043:Motor Activity / Q000502:physiology / Q000528:radiation effects; D017111:Phodopus / Q000235:genetics / Q000502:physiology*; D017440:Photoperiod; D017027:Protein Tyrosine Phosphatases / Q000235:genetics; D044094:Receptors, Melatonin / Q000235:genetics; D012098:Reproduction / Q000502:physiology / Q000528:radiation effects; D012621:Seasons; D013087:Spermatids / Q000502:physiology; D013094:Spermatozoa / Q000502:physiology
chemical_list: D007028:Hypothalamic Hormones; D008070:Lipopolysaccharides; D044094:Receptors, Melatonin; D007987:Gonadotropin-Releasing Hormone; D017027:Protein Tyrosine Phosphatases
keywords: 2,4-dinitro-1-flourobenzene; DNFB; DTH; Eya3; Eyes absent 3; GnIH; GnRH; Immune function; LD; LPS; Light pollution; PT; Pelage; Per1; Period1; Photoperiodism; RFRP; RFamide-related peptide; SCN; SD; Seasonality; TSH; TSH receptor; TSHR; dLAN; delayed-type hypersensitivity; dim light at night; gonadotropin-inhibiting hormone; gonadotropin-releasing hormone; lipopolysaccharide; long days; pars tuberalis; short days; suprachiasmatic nuclei; thyroid-stimulating hormone