Abstract
Objectives
The human body physiology rapidly changes and adapt to several environmental stimuli, including light. Abnormal artificial light exposures have been shown to affect sleep cycle, cognition, and mood. Although studies have reported inconsistent effects of short-term or constant long-term light exposures, human exposures to artificial lights occur at varying, unpredictable times and duration daily. Here, we studied the effects of long-term unpredictable light exposure on learning, memory, oxidative status, and associated cytokines in rats.
Methods
Artificial lighting was provided using an array of white light-emitting diodes coupled to a microcontroller that switches them on or off at unpredictable times and duration (light intensity = 200 ± 20 lx). Within the last eight days of 40 days exposure, animals were subjected to open field test, Morris water maze, and novel object recognition behavioral paradigms. Brain levels of malondialdehyde (MDA), superoxide dismutase (SOD), catalase, reduced glutathione (GSH), glutathione S-transferase (GST), tumor necrosis factor-alpha (TNF-α), and vascular endothelial growth factor (VEGF) were assayed.
Results
Exposed rats showed impaired spatial learning and memory (p<0.05), but no changes in object recognition memory or locomotor activity. Oxidative stress analyses also revealed significant changes in the concentrations of MDA, SOD, catalase, and GSH levels (p<0.05), not GST. Similarly, there was an increased TNF-α expression (p<0.05), not VEGF.
Conclusions
We conclude that oxidative stress is involved in memory impairment in rats exposed to prolonged unpredictable lights, which again suggests the detrimental effects of extended light exposure on the nervous system.
Acknowledgments
The authors would like to appreciate Aremu J.O and Okpanachi O.O of the Department of Computer Science and Human Physiology, Bingham University respectively, for their technical assistance.
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Research funding: None declared.
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Author contributions: All authors have accepted responsibility for the entire content of this manuscript and approved its submission.
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Competing interests: Authors state no conflict of interest.
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Ethical approval: The local Institutional Review Board deemed the study exempt from review. All experimental procedures on rodents in the study were conducted following established protocols under the guidelines of the Principle of Laboratory Animal Care (National Institute of Health). At the time of the experimentation, the institution generally exempt studies with fewer animals from review. The study has indeed adhered to these guidelines as the number of animals was significantly reduced and refined that no invasive procedures were employed. Stress was significantly reduced, and no pain was inflicted throughout the experimentation.
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