Mistimed exposure to light has been demonstrated to negatively affect multiple aspects of physiology and behavior. Here we analyzed the effects of chronic exposure to abnormal lighting conditions in mice. We exposed mice for 1 year to either: a standard light/dark cycle, a “light-pollution” condition in which low levels of light were present in the dark phase of the circadian cycle (dim light at night, DLAN), or altered light cycles in which the length of the weekday and weekend light phase differed by 6 h (“social jetlag”). Mice exhibited several circadian activity phenotypes, as well as changes in motor function, associated particularly with the DLAN condition. Our data suggest that these phenotypes might be due to changes outside the core clock. Dendritic spine changes in other brain regions raise the possibility that these phenotypes are mediated by changes in neuronal coordination outside of the clock. Given the prevalence of artificial light exposure in the modern world, further work is required to establish whether these negative effects are observed in humans as well.

DTNBP1 is a gene associated with schizophrenia. Postmortem studies found a reduced expression of DTNBP1 in regions associated with schizophrenia in patients’ brains. Sandy (Sdy) mice have a loss-of-function mutation in Dtnbp1 gene, resulting in behavioral deficits and brain changes similar to those seen in patients with schizophrenia. We previously showed that exposing adult Sdy mice to circadian disruption led to an exacerbation of schizophrenia-relevant behaviors. Here we asked whether the interaction between this genetic risk factor and circadian disruption occurs during adolescence, a period when environmental insults can promote schizophrenia symptoms, and whether sex affects this interaction. Starting at postnatal day 21, wild-type (WT) and Sdy males and females were housed for 4 weeks either in a 12 h light:12 h dark (LD 12:12) cycle or under chronic jetlag (CJL). Then, after 2 weeks in LD 12:12, behavioral assessments were conducted, including elevated plus maze (EPM), novel object recognition (NOR), social interaction, and prepulse inhibition (PPI) of acoustic startle. NOR and social novelty tests showed that, surprisingly, CJL during adolescence had opposite effects on WT and Sdy males, that is, behavioral deficits in WT males while rescuing preexisting deficits in Sdy mice. CJL led to decreased sociability in WT and Sdy mice while decreasing PPI only in females. Sdy mice showed decreased anxiety-like behavior compared with wild-type (WT), which was further accentuated by CJL in males. Thus, circadian disruption during adolescence, on its own or in association with Dtnbp1 mutation, can influence cognition, sociability, sensorimotor gating, and anxiety-like behaviors in a sex-dependent manner.

No abstract