Turkish Journal of Biology




The pineal hormone melatonin is known to play an important role in mediating photoperiodic messages to the reproductive system in seasonal breeding animals. In this study, we investigated whether a 1 h subcutaneous infusion of 50 ng of melatonin at 2000-2100 hours, effective in causing inhibition of testicular development in the juvenile Siberian hamsters (Phodopus sungorus), would cause testicular regression in adults of this species housed on a long photoperiod (LD16:8). Pinealectomized adult hamsters received programmed subcutaneous infusions of 50 or 500 ng of melatonin or vehicle (0.12 ml) at 2000-2100 hours each day for 8 weeks. We found that the testicular weights of infused animals receiving melatonin or vehicle were not different from each other; all animals retained large testes. These results show that a 50 ng melatonin infusion at a particular time point (2000-2100 hours) is not effective in altering the functional status (size) of the testes of adults.


Melatonin, Siberian hamster, Photoperiod, Testes, Infusion

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