Short and long photoperiods differentially exacerbate corticosterone-induced physical and psychological symptoms in mice.

In this study, we analyzed the effects of daily light/dark (LD) conditions on depression and other symptoms, and also analyzed the mixed effects of LD conditions and corticosterone treatment. Male adult C57BL/6 mice were treated with corticosterone in a normal LD cycle of 12 hours light and 12 hours dark (LD12 : 12), short day conditions of 6 hours light and 18 hours dark (LD6 : 18), or long day conditions of 21 hours light and 3 hours dark (LD21 : 3). The activity rhythms of mice in aberrant LD conditions were entrained within 2 weeks. After 6 weeks of exposure, several behavioral tests were conducted. Corticosterone induced body weight gain and depression-like symptoms. The short or long LD conditions had little effect on vehicle-treated mice behavior. However, the aberrant LD conditions exacerbated the corticosterone-induced symptoms. Mice treated with corticosterone in LD6 : 18 showed exacerbated depression-like symptoms in a novelty suppressed feeding test. On the other hand, LD21 : 3 did not show any effects on mood, but enhanced corticosterone-induced body weight gain. These results indicated that aberrant LD conditions could act as an exacerbating factor for corticosterone-induced symptoms, and that short and long photoperiods induce different psychological and physiological changes. This corticosterone + aberrant LD model could be a useful animal model for investigating the effect of LD conditions on depression, obesity, and other symptoms in stressful circumstances....
Source: Biomed Res - Category: Research Authors: Tags: Biomed Res Source Type: research