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

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.

Quantitative and qualitative analysis of rat pup ultrasonic vocalization sounds induced by a hypothermic stimulus / 한국실험동물학회지

Ultrasonic vocalizations (USVs) are essential communicative sounds used between rodent pups and their mother. Rat pups emit USVs in stressful situations, such as when they are cold or separated from the nest. We verified the ontogenetic changes in USVs emitted by infant rats isolated from their mother during the pre-weaning period. The number of calls, and the median frequency and first peak of frequency of the calls were measured at 1, 3, 5, 7, 10, 12, and 14 days postnatal age in Wistar-Imamichi rats. Pups were placed in a cold glass beaker and USVs were recorded for 5 min. The number of calls increased to a peak on day 5 and then gradually decreased. The median frequency of calls decreased slowly during the first 12 days, and then increased slightly on day 14. Similarly, the first peak frequency of calls was the highest on day 1, and then decreased gradually by day 12. A small increase was observed on day 14. These changes in frequency were correlated with the physical development of the pups, whose body weights increased significantly with age except during postnatal days 7-10.

Effects of estrogen on food intake, serum leptin levels and leptin mRNA expression in adipose tissue of female rats / 한국실험동물학회지

The integration of metabolism and reproduction involves complex interactions of hypothalamic neuropeptides with metabolic hormones, fuels, and sex steroids. Of these, estrogen influences food intake, body weight, and the accumulation and distribution of adipose tissue. In this study, the effects of estrogen on food intake, serum leptin levels, and leptin mRNA expression were evaluated in ovariectomized rats. Seven-week-old female Wistar-Imamichi rats were ovariectomized and divided into three treatment groups: group 1 (the control group) received sesame oil, group 2 was given 17beta-estradiol benzoate, and group 3 received 17beta-estradiol benzoate plus progesterone. The body weight and food consumption of each rat were determined daily. Serum leptin levels and leptin mRNA expression were measured by ELISA and quantitative RT-PCR, respectively. Food consumption in the control group was significantly higher (P<0.05) than that in groups 2 and 3, although body weight did not significantly differ among the three groups. The serum leptin concentration and leptin mRNA expression were significantly higher (P<0.05) in groups 2 and 3 than in group 1, but no significant difference existed between groups 2 and 3. In conclusion, estrogen influenced food intake via the modulation of leptin signaling pathway in ovariectomized rats.