Diurnal Gain And Nocturnal Reduction Of Body Weight In Young Adult Rabbits: The Reverse Of The Circadian Rhythm Observed In Rats And Mice

Abstract

Citation: Kawamura S, Yamazoe H, Hosokawa Y (2020) Diurnal Gain and Nocturnal Reduction of Body Weight in Young Adult Rabbits: The Reverse of the Circadian Rhythm Observed in Rats and Mice. J Toxicol Cur Res 4: 016. Abstract Understanding circadian rhythms in experimental animals is im-portant to comprehensively evaluate animal responses to chemical exposure and gain deep insight into the pharmacological and toxico- logical effects of chemical exposure. Animals may respond different-ly to chemical exposure at different time points because many bodily functions have daily rhythms. In rats and mice, major experimental animals used in toxicology studies, circadian changes in physi- ological parameters including body weight, food consumption and hormones have been reported. In rabbits, the other principal experimental animal in teratology, circadian rhythms of behavioural functions such as physical activity and food intake, but not body weight change, have been described. To better understand fundamental biological characteristics of rabbits, we measured body weight and food consumption of male and female rabbits of two strains in the morning and evening for several days, calculating diurnal and nocturnal body weight changes and food intake per hour during the interval. Rabbits as well as rats and mice ate more at night than during the day. Nevertheless, rabbits showed diurnal increase and nocturnal decrease of body weight. This is the reverse of the circadian change observed in rats and mice. There was no strain-specific difference in the circadian rhythms in body weight and food consumption in rabbits. Male and female rabbits showed a similar daily rhythm in body weight and food consumption. In conclusion, there was a remark-able species difference in circadian rhythm in body weight between rats and rabbits.