Light interference and melatonin affects digestion and glucocorticoid metabolites in striped mouse

Abstract

Animals secrete glucocorticoids to deal with daily stressors. Studies have found that supplemental melatonin decreases glucocorticoid metabolite levels in stressed animals. We determined the effect of light interference (LI) and supplemental melatonin on (1) body mass, (2) food intake and (3) glucocorticoid metabolite levels of the striped mouse (Rhabdomys pumilio). Experiment was split into three phases: 8 L: 16 D; 8 L: 16 D with a 15 min light interruption every 4 h; and 8 L: 16 D with a 15 min light interruption every 4 h and melatonin (0.2 μg/ml) added to the water. Body mass was significantly different between phases with lowest body mass (89.17 ± 6.56 g) occurring during standard 8 L: 16 D. LI and melatonin significantly increased body mass. LI increased and melatonin decreased glucocorticoid metabolite levels. LI significantly increased and melatonin significantly decreased assimilation efficiencies possibly due to changes in energetic demands.

Keywords:

• glucocorticoid
• light at night
• melatonin
• Rhabdomys pumilio
• rodent
• stressor

Acknowledgements

Amy-Leigh Wilson would like to thank the National Research Foundation for financial assistance for this study. We thank Petra Wester for kindly lending us “her” mice; Adam Shuttleworth for his valuable advice, proofreading and assistance with building cages and data collection; and Mark Brown, the Animal House and Thami Mjwara for housing and caring for the mice. Ethical clearance for this study was approved by the Animal Ethics sub-committee of the UKZN.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the National Research Foundation [grant number 88204].