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The Effects of Constant Light and Running-Wheel Access in Middle-Aged Female C57BL6/J Mice
Fernanda Medeiros Contini1, Samantha G Burke2, John C Price2
1Department of Neurobiology, Harvard Medical School, Boston, MA, United States.
Objective Chronic light exposure is associated with poorer mental and physical health. Many groups are chronically exposed to light due to their work schedule, including night-shift nurses. The present study aims to determine if middle-aged female mice have an increased vulnerability to chronic light exposure compared with younger individuals. Materials and Methods Young and middle-age female mice were housed in cages with or without running wheels and were exposed to either a 12:12-hour light:dark cycle or constant light (LL). All mice were assayed for circadian locomotor activity and anxiety-like behaviors, and weight, food consumption, and estrogen receptor beta (ERβ) levels were measured. Results Middle-aged mice exhibited longer circadian periods in LL, reduced circadian power, and increased food consumption compared with young mice. LL increased novelty-induced activity and reduced ERβ regardless of age. Discussion These results indicate that middle-aged females may have an increased susceptibility to the negative circadian consequences caused by constant bright light exposure.
Objective Chronic light exposure is associated with poorer mental and physical health. Many groups are chronically exposed to light due to their work schedule, including night-shift nurses. The present study aims to determine if middle-aged female mice have an increased vulnerability to chronic light exposure compared with younger individuals. Materials and Methods Young and middle-age female mice were housed in cages with or without running wheels and were exposed to either a 12:12-hour light:dark cycle or constant light (LL). All mice were assayed for circadian locomotor activity and anxiety-like behaviors, and weight, food consumption, and estrogen receptor beta (ERβ) levels were measured. Results Middle-aged mice exhibited longer circadian periods in LL, reduced circadian power, and increased food consumption compared with young mice. LL increased novelty-induced activity and reduced ERβ regardless of age. Discussion These results indicate that middle-aged females may have an increased susceptibility to the negative circadian consequences caused by constant bright light exposure.
