Effects of photoperiod and temperature on the body mass, thermogenesis, and serum leptin levels of Apodemus draco (Rodentia: Muridae) in the Hengduan Mountain region, China

Background: Environmental cues play important roles in the regulation of physiology and behavior in small mammals. In the present study, we performed a factorial experiment (temperature x photoperiod) in which the South China field mouse Apodemus draco (Rodentia: Muridae) was acclimated to different photoperiods (a long photoperiod of 16 h light/8 h dark and a short photoperiod of 8 h light/16 h dark) and temperatures (warm at 30 degrees C and cold at 5 degrees C) to test the hypothesis that photoperiod, temperature, or both together can trigger changes in serum leptin levels, body mass, thermogenesis, and energy intake. Results: Body mass, the resting metabolic rate (RMR), nonshivering thermogenesis (NST), and energy intake significantly decreased in the cold condition. Cold exposure induced increases in mitochondrial protein contents, cytochrome C oxidase (COX) activity, and a-glycerophosphate oxidase (a-GPO) in the liver and brown adipose tissue (BAT). There were no significant differences in mitochondrial protein contents, COX, or a-GPO under different photoperiods. Cold also induced an increase in uncoupling protein 1 in the BAT but showed no significant differences with photoperiod. Conclusions: All of the results indicated that A. draco was more sensitive to temperature. Further,serum leptin levels were involved in the processes of thermogenesis and body mass regulation in A. draco.