Maternal programming of the fetal brain dictates the response of juvenile Siberian hamsters to photoperiod: Dissecting the information transfer system

Development of neuroendocrine mechanisms regulating reproduction results from the interaction between genetic and environmental factors. For the developing fetus, the environment includes the maternal system. Our work with Siberian hamsters examines mechanisms by which prenatal photoperiods influence neuroendocrine functions regulating postnatal reproductive development. The maternal system has two effects on the young: (1) to program a reproductive growth pattern in the young and (2) to influence the ability of the young to respond to photoperiods encountered after weaning. Three paradigms have been used to study the role of the pineal hormone melatonin in this process. Injection of pregnant females with melatonin or removing melatonin has demonstrated that the maternal pineal is required for the transference of photo‐periodic information to fetuses. However, when pregnant females receive continuous release implants of melatonin the effects of melatonin on fetuses are dependent on gestational photoperiod, suggesting that while melatonin is necessary it is not the only component in the mechanism for the transference of photoperiodic information to fetuses.