Increased anxiety-like behavior but no cognitive impairments in adult rats exposed to constant light conditions during perinatal development

Abstract

Background. Shift-work is suggested to affect fetal development negatively. In particular, maternal hormonal disturbance arising from sleep deprivation or circadian rhythm changes may disturb fetal growth or lead to complications during pregnancy. Exposure to constant light is an environmental stressor that can affect the circadian system and has been shown to induce neurochemical and behavioral changes when used during the prenatal and/or postnatal period in experimental animals. However, studies investigating long-term effects of constant light in the offspring are sparse.

Methods. An accidental power outage resulted in pregnant females being housed under constant light (LL) conditions for seven days of the offspring perinatal development (embryonic day 20 to postnatal day 4). The long-term effects of constant light on the behavior in the adult offspring were assessed by means of open field, object recognition, and water maze tests.

Results. In adulthood, LL-animals displayed an intact recognition memory and no deficits in spatial learning or memory. In the open field test, LL-animals exhibited higher anxiety-like behavior, observed as significantly more thigmotaxis and less ambulation. These results were confirmed in the other behavioral tests as the LL-animals spent less time exploring the objects in the object recognition test, and showed thigmotactic behavior also in the water maze test.

Conclusion. The results confirm that early life experience can cause changes in brain development that shape brain function and add to the sparse literature on long-term effects of constant light conditions during perinatal development on specific behaviors in adulthood.

Key words::

• Anxiety
• biological rhythms
• circadian rhythm
• cognitive function
• development
• open field
• shift-work
• stress
• water maze

Acknowledgements

Ms Marita Berg, Professor Eva Brittebo, and Dr Samuel Rowley Uppsala University are gratefully acknowledged for technical assistance, for valuable comments during the preparation of the manuscript, and for language editing, respectively.

Declaration of interest: Funding from the Swedish Society for Medical Research (E.R.), the Facias Foundation (E.R. and O.K.), the Helge Ax:son Johnson Foundation (O.K.), and NN Jubileumsfond B (O.K.) supported this study. The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.