Reproductive Development of Japanese Quail (Coturnix coturnix japonica) in Males and Females Subjected to Leptin Injections

The goal of this study was to determine when leptin was most effective as a hormone and to clarify the role of leptin in sexual development in Japanese quails (Coturnix coturnix japonica). In the initial study, we compared the effects of long and short photoperiods on the daily plasma leptin levels of adult males. Leptin levels were assessed in blood collected at 12:00, 16:00, 20:00, 00:00, 04:00, and 08:00 hours throughout the course of 24 hours. The second experiment investigated how different leptin dosages influenced the development of sexual maturity in juveniles. Six-day old quails that had hatched from the eggs were divided into four groups (control, 0.1 mu g, 1.0 mu g, and 4.0 mu g leptin) and given daily injections at daytime and nighttime under long photoperiod until puberty. Body weight, testosterone, and estradiol levels were determined. It was found that leptin had a distinct daily rhythm, with low levels throughout the day and higher levels at night. Leptin had a dose-dependent impact that accelerated pubertal development; this effect was particularly obvious in quails that received injections at night. The findings suggest that leptin may be important for sexual development and that the timing of leptin treatment has an impact on puberty.