Maternal transfer of photoperiodic information in Siberian hamsters. II. The nature of the maternal signal, time of signal transfer, and the effect of the maternal signal on peripubertal reproductive development in the absence of photoperiodic input.
Peripubertal reproductive development of Siberian hamsters is controlled by maternally derived photoperiodic information and the ambient photoperiod present after weaning. Previous experiments suggested that the maternally derived information is transferred during gestation, not during lactation. Development was examined in several photoperiods following manipulation of gestational and lactational photoperiods; development was influenced by the gestational, but not lactational, photoperiod. Second, effects of the gestational photoperiod were observed in young reared in constant light (LL) from Day 15. Depriving the young of ambient photoperiodic information after Day 15 allows a more direct assessment of the signal received from their dams. Finally, melatonin injections to long-day dams, at certain times of day, caused transmission of a short-day signal to young, as evidenced by their development in LL and light-dark cycles. Thus, a maternally derived signal that is dependent on melatonin influences reproductive development of the young during gestation; the maternally directed pattern of development can subsequently be modified by the youngs' own response to ambient photoperiods after weaning.