The effect of circadian-disrupting environments on sleep and binge-like eating behavior. - Project Summary/Abstract The brain both encodes information to drive normative functions and decodes abnormal information to navigate sustenance and homeostasis in suboptimal conditions. This regulatory role is strongly influenced by the body’s circadian rhythms that link the light-dark cycle of our planet with internal physiology. We do not yet understand how the brain translates disruptions to the light-dark cycle (e.g., from our industrial environments that can have light during the biological night) to regulate two fundamental behaviors required for life: sleep timing and eating, both of which are circadian-regulated. One recent approach to this problem (from the Richardson lab) is the fragmented day-night (FDN) model, in which within each 24-hour cycle, there are four cycles of 4 hr Light + 2 hr Dark (4:2 LD) (total 16:8 LD in 24 hrs). The mode of introduction of this light-dark protocol (suddenly: FDN-S or gradually: FDN-G) determined dramatically different phenotypes of locomotion in mice, even though the resulting light-dark environments are identical. This suggests that the brain modifies behavior to the same environment based on how the environment is presented. We hypothesize that the FDN-S and FDN-G environments will also differentially (i) negatively impact sleep and eating behavior timing and (ii) change neuronal activation and gene expression in key brain regions. To address these hypotheses, we ask the following questions: Compared to consolidated 16 hours of light and consolidated 8 hours of darkness (i.e., Control), 1) How is sleep timing, a major restorative circadian-driven behavior, affected by the FDN-S vs FDN-G environments? 2) How is eating behavior timing, which is circadian-regulated, be impacted during FDN-S and FDN-G environments when mice are challenged with a binge-eating paradigm? 3) Is there a difference in neuronal activation and gene expression levels in FDN-S vs FDN-G in brain regions involved in sleep and eating behavior timing? We will accomplish our goals using (i) the PiezoSleep Mouse Behavioral Tracking System to record sleep, (i) the binge-eating test to study eating behavior, (iii) c-fos immunohistochemistry to study neuronal activation, and (iv) dPCR for gene expression using wildtype (WT- C57BL/6NCrl) adult male and female mice. The brain areas of focus associated with sleep and circadian-regulated eating behavior will be the suprachiasmatic nucleus (circadian light-response), ventrolateral preoptic nucleus (sleep initiation), lateral habenula (stress- related induction of sleep), paraventricular nucleus (stress/eating behavior) and arcuate nucleus (eating behavior). This study is innovative because it uses the same amount of light and dark exposure within 24 hours to yield three activity patterns. This work is crucial for understanding how the brain responds to the same stimulus (e.g., light) depending on how the stimulus is presented (specific LD cycles). Together with the 3-year development plan, the proposed study will serve as a unique research experience for the talented undergraduate students at Oakwood University on topics integral to their daily lives: light, sleep, and eating.
