Reproductive Response of Adult Siberian Hamsters to One-Hour Melatonin Infusions

Authors: BÜLENT GÜNDÜZ, MILTON H. STETSON

Abstract: 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.

Keywords: Melatonin, Siberian hamster, Photoperiod, Testes, Infusion

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