B. Gunduz et Mh. Stetson, The impact of photoperiods and melatonin on gonadal development in juvenile Turkish hamsters (Mesocricetus brandti), J PINEAL R, 25(4), 1998, pp. 193-200
The reproductive response of both intact adult and juvenile Turkish hamster
s has been thoroughly studied and shown to be similar, unlike the golden ha
mster where juveniles remain aphotoperiodic until approximately 8 weeks of
age. Unstudied to date, however, is the role of the pineal and its hormone
melatonin in generating the testicular response to photoperiod in juvenile
Turkish hamsters. Therefore, in this study we examined the reproductive res
ponse of prepubertal male Turkish hamsters, subjected to four different pho
toperiods (8L:16D, 16L:8D, 20L:4D, and 24L:OD) with altered pineal gland fu
nction. At 15 days of age, long-day-born (16L:8D) hamsters were either pine
alectomized, received melatonin implants, or remained untreated. Testes siz
es were measured every 2 weeks. Testicular growth occurred only in untreate
d and beeswax implanted groups in 16L:8D, Exposure to other photoperiods in
hibited testicular development in untreated and beeswax implanted animals.
Removal of the pineal gland, masking of the daily melatonin rhythm with con
stant release subcutaneous melatonin implants, or eliminating the daily rhy
thm of melatonin by continuous light exposure resulted in inhibition of gon
adal development. These results demonstrate that juvenile Turkish hamsters
respond similarly to adults on all photoperiods and under all conditions of
pineal function tested.