Influence of Subcutaneous Melatonin Implantation on Gonadal Development and on Plasma Levels of Luteinizing Hormone, Testosterone, Estradiol, and Corticosterone in the Pigeon

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Abstract
Subcutaneous implantation of melatonin for a period of 12 weeks with reinforcement of implants every fortnight had no significant influence on photoinduced gonadal development in the pigeon. Neither the weight of the gonads or the oviduct nor the gonadal size was affected by melatonin. Pinealectomy also was found to have no significant influence on gonadal weight when examined 20 weeks after the surgery. The plasma levels of luteinizing hormone and testosterone were not significantly influenced by a 10-week implantation of melatonin, although a trend toward an increase (statistically insignificant) in testosterone concentration was apparent in melatonin-implanted male pigeons. Plasma concentration of estradiol was found to increase significantly in both male and female pigeons following the 10-week melatonin implantation. A trend toward an increase in plasma corticosterone level was also apparent in these melatonin-implanted birds, but the increase was statistically insignificant.