Irregular light schedules induce alterations on daily rhythms and gene expression in mice

Synchronization of internal biological rhythms with external light-dark cycles is crucial for proper function and survival of the organisms, however modern life often imposes irregular light exposure, disrupting these internal clocks. This study investigated the effects of short-term shifted light-dark cycles on mice rhythmicity, and whether these alterations trigger molecular or behavioral changes. We evaluated locomotor activity, different behavioral domains and gene expression in the hypothalamus and medial prefrontal cortex. Despite non prominent behavioral impairments, such as anxiety or cognitive deficits, we observed a notable simplification in the locomotor activity patterns of the mice subjected to disrupted light-dark cycles. Molecular alterations included dysregulations in oscillations of core clock genes (Cry2, Per2) and disruptions in expression of genes involved in neuroplasticity, motivation, and stress responses, including GluA1, Crhr2, and Vip in both studied brain areas. Our study reveals that even brief light cycle shifts can disrupt circadian regulation at the molecular level, despite minimal behavioral changes. This molecular-behavioral discrepancy may suggest a complex adaptive response to drastic short-term light perturbations. Understanding the complex interplay between external light cues and internal biological rhythms regulation is crucial for mitigating the negative consequences of irregular light exposure on physiological processes and overall well-being.