Lab Anim Res.  2013 Mar;29(1):1-6.

Serum leptin concentrations, leptin mRNA expression, and food intake during the estrous cycle in rats

  • 1Behavioral Neuroscience Laboratory, Graduate School of Veterinary Medicine, Nippon Veterinary and Life Science University, Tokyo, Japan.
  • 2Laboratory of Animal Physiology, Nippon Veterinary and Life Science University, Tokyo, Japan.
  • 3Department of Laboratory Animal science, Dokkyo University School of Medicine, Tochigi, Japan.
  • 4Faculty of Pharmaceutical Sciences, University of Iceland, Reykjavik, Iceland.
  • 5Department of Experimental Medicine, University of Copenhagen, Copenhagen, Denmark.
  • 6Department of Veterinary Anatomy, College of Veterinary Medicine, Chonnam National University, Gwangju, Korea.
  • 7Department of Zoology, Faculty of Science, Kasetsart University, Bangkok, Thailand.


The aim of this study was to investigate food intake, serum leptin levels, and leptin mRNA expression during the sexual cycle in rats. Female Wistar-Imamichi rats aged 8-10 weeks were used in this experiment. Food intake was measured during the light and dark phases (light on at 07:00 and off at 19:00) of the 4-day estrous cycle in female rats. Serum leptin levels were measured by ELISA, and leptin mRNA expression levels were analyzed using real-time PCR on diestrous- and proestrous-stage rats. Our results revealed that during the sexual cycle, food intake was significantly higher in the dark phase compared with the light phase. Food intake in proestrous females was significantly lower in the light and dark phases compared with the other groups. Serum leptin concentrations were significantly higher in both phases in proestrous rats compared with diestrous rats. There was a significant increase in leptin mRNA expression in adipose tissue during the proestrous period compared with the diestrous period. These findings suggest that increased leptin mRNA expression and serum leptin levels, which are induced by estrogen during the proestrous stage, may play a role in regulating appetitive behavior.


Estrous cycle; food intake; leptin
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