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Author Shuboni, D; Yan, L url  doi
openurl 
  Title Nighttime dim light exposure alters the responses of the circadian system Type Journal Article
  Year 2010 Publication (up) Neuroscience Abbreviated Journal  
  Volume 170 Issue 4 Pages 1172-1178  
  Keywords animals; rodents; animal behaviour: human physiology  
  Abstract The daily light dark cycle is the most salient entraining factor for the circadian system. However, in modern society, darkness at night is vanishing as light pollution steadily increases. The impact of brighter nights on wild life ecology and human physiology is just now being recognized. In the present study, we tested the possible detrimental effects of dim light exposure on the regulation of circadian rhythms, using CD1 mice housed in light/dim light (LdimL, 300 lux:20 lux) or light/dark (LD, 300 lux:1 lux) conditions. We first examined the expression of clock genes in the suprachiasmatic nucleus (SCN), the locus of the principal brain clock, in the animals of the LD and LdimL groups. Under the entrained condition, there was no difference in PER1 peak expression between the two groups, but at the trough of the PER 1 rhythm, there was an increase in PER1 in the LdimL group, indicating a decrease in the amplitude of the PER1 rhythm. After a brief light exposure (30 min, 300 lux) at night, the light-induced expression of mPer1 and mPer2 genes was attenuated in the SCN of LdimL group. Next, we examined the behavioral rhythms by monitoring wheel-running activity to determine whether the altered responses in the SCN of LdimL group have behavioral consequence. Compared to the LD controls, the LdimL group showed increased daytime activity. After being released into constant darkness, the LdimL group displayed shorter free-running periods. Furthermore, following the light exposure, the phase shifting responses were smaller in the LdimL group. The results indicate that nighttime dim light exposure can cause functional changes of the circadian system, and suggest that altered circadian function could be one of the mechanisms underlying the adverse effects of light pollution on wild life ecology and human physiology.  
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  Call Number LoNNe @ schroer @ Serial 1601  
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Author Ikeda, Masayuki; Sagara, Masami; Inoué, Shojiro url  doi
openurl 
  Title Continuous exposure to dim illumination uncouples temporal patterns of sleep, body temperature, locomotion and drinking behavior in the rat Type Journal Article
  Year 2000 Publication (up) Neuroscience Letters Abbreviated Journal  
  Volume 279 Issue 3 Pages 185-189  
  Keywords animals; rodents; animal behaviour  
  Abstract Dissociable circadian rhythms of sleep and body temperature in primates are thought to be regulated by independent oscillators whereas the uncoupling of circadian rhythms has not been well described in other mammals. Therefore, we made simultaneous recordings of non-rapid-eye-movement-sleep (NREMS), rapid-eye-movement-sleep (REMS), brain temperature, intraperitoneal temperature, locomotion and drinking activity under light-dark (LD) and continuous dim illumination (dim LL) and analyzed their interrelations. The rhythmic patterns of body temperature, locomotion and drinking were modified on the 12th circadian day of dim LL, while the mean body temperature as well as mean occurrence of drinking and locomotor activities did not change significantly. In contrast, dim LL exposure significantly increased the total time spent in NREMS during the resting phase of dim LL and increased REMS episodes during the active phase of dim LL. The diverse effects of dim LL exposure on the recorded phenomena suggest that temporal patterns of sleep were the most sensitive to perturbations of lighting and that differential oscillatory mechanisms may regulate sleep and other circadian rhythms in the rat.  
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  Notes Approved no  
  Call Number LoNNe @ schroer @ Serial 1591  
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