Home | << 1 >> |
![]() |
Fonken, L. K., Finy, M. S., Walton, J. C., Weil, Z. M., Workman, J. L., Ross, J., et al. (2009). Influence of light at night on murine anxiety- and depressive-like responses. Behav Brain Res, 205(2), 349–354.
Abstract: Individuals are increasingly exposed to light at night. Exposure to constant light (LL) disrupts circadian rhythms of locomotor activity, body temperature, hormones, and the sleep-wake cycle in animals. Other behavioural responses to LL have been reported, but are inconsistent. The present experiment sought to determine whether LL produces changes in affective responses and whether behavioural changes are mediated by alterations in glucocorticoid concentrations. Relative to conspecifics maintained in a light/dark cycle (LD, 16:8 light/dark), male Swiss-Webster mice exposed to LL for three weeks increased depressive-like behavioural responses as evaluated by the forced swim test and sucrose anhedonia. Furthermore, providing a light escape tube reversed the effects of LL in the forced swim test. LL mice displayed reduced anxiety as evaluated by the open field and elevated-plus maze. Glucocorticoid concentrations were reduced in the LL group suggesting that the affective behavioural responses to LL are not the result of elevated corticosterone. Additionally, mice housed in LD with a clear tube displayed increased paired testes mass as compared to LL mice. Taken together, these data provide evidence that exposure to unnatural lighting can induce significant changes in affect, increasing depressive-like and decreasing anxiety-like responses.
Keywords: Human Health; Animals; Anxiety/*physiopathology; Corticosterone/blood; Depression/*physiopathology; Dietary Sucrose/administration & dosage; Drinking Behavior/physiology; Light/*adverse effects; Lighting; Locomotion/physiology; Male; Maze Learning; Mice; Neuropsychological Tests; Organ Size; Photic Stimulation; *Photoperiod; Random Allocation; Swimming; Testis/pathology
|
Fonken, L. K., Kitsmiller, E., Smale, L., & Nelson, R. J. (2012). Dim nighttime light impairs cognition and provokes depressive-like responses in a diurnal rodent. J Biol Rhythms, 27(4), 319–327.
Abstract: Circadian disruption is a common by-product of modern life. Although jet lag and shift work are well-documented challenges to circadian organization, many more subtle environmental changes cause circadian disruption. For example, frequent fluctuations in the timing of the sleep/wake schedule, as well as exposure to nighttime lighting, likely affect the circadian system. Most studies of these effects have focused on nocturnal rodents, which are very different from diurnal species with respect to their patterns of light exposure and the effects that light can have on their activity. Thus, the authors investigated the effect of nighttime light on behavior and the brain of a diurnal rodent, the Nile grass rat. Following 3 weeks of exposure to standard light/dark (LD; 14:10 light [~150 lux] /dark [0 lux]) or dim light at night (dLAN; 14:10 light [~150 lux] /dim [5 lux]), rats underwent behavioral testing, and hippocampal neurons within CA1, CA3, and the dentate gyrus (DG) were examined. Three behavioral effects of dLAN were observed: (1) decreased preference for a sucrose solution, (2) increased latency to float in a forced swim test, and (3) impaired learning and memory in the Barnes maze. Light at night also reduced dendritic length in DG and basilar CA1 dendrites. Dendritic length in the DG positively correlated with sucrose consumption in the sucrose anhedonia task. Nighttime light exposure did not disrupt the pattern of circadian locomotor activity, and all grass rats maintained a diurnal activity pattern. Together, these data suggest that exposure to dLAN can alter affective responses and impair cognition in a diurnal animal.
Keywords: Analysis of Variance; Animals; CA1 Region, Hippocampal/cytology; CA3 Region, Hippocampal/cytology; Circadian Rhythm/*physiology; Cognition/*physiology/radiation effects; Corticosterone/blood; Dendrites/physiology/radiation effects; Dentate Gyrus/cytology; Depressive Disorder/*physiopathology; Food Preferences/physiology/radiation effects; Light; Male; Maze Learning/physiology/radiation effects; Motor Activity/physiology/radiation effects; Murinae/*physiology; Neurons/drug effects/physiology; *Photoperiod; Swimming/physiology
|