The effects of ovariectomy on the behavioral and physiological responses to constant light in C57BL6/J Mice

Abstract

ABSTRACT Circadian disruptions, including exposure to constant light, are known to produce behavioral and physiological issues. However, sex differences exist in how those problems manifest, as males tend to have increased susceptibility to the negative consequences of circadian disruption. As gonadal hormones play a role in circadian timekeeping, we decided to investigate whether ovariectomized C57BL6/J mice would exhibit increased behavioral and physiological sensitivity to constant light compared to female mice with intact estrogen circulation. Mice, half of which underwent an ovariectomy and the other half received sham surgery, were then placed in either constant light or a 12:12 light-dark cycle. After six weeks of photoperiod exposure, we measured their circadian locomotor activity, anxiety-like behaviors and physiological responses. Mice which underwent ovariectomy and placed into constant light experienced altered glucose levels and reduced robustness of the circadian rhythm, with some becoming arrhythmic, compared to sham surgery animals in constant light. Additionally, ovariectomy led to delayed circadian activity onsets and reduced both home-cage and novelty-induced activity. Meanwhile, constant light produced increases to ambulatory activity in the behavioral assays and reduced circadian home-cage activity. These results indicate that removal of the ovaries can mediate the circadian, behavioral, and physiological responses to continuous light.