Most species have evolved reproductive strategies to insure that offspring are born during a time of year that provides maximum survival potential. Length of day supplemented by other environmental cues are used to predict these times. Although much progress has been made in understanding how photoperiodic information is perceived by animals, the tranduction of this information to hormonal signals that control reproductive function is still not well understood. The overall objectives of these studies is to identify brain mechanisms by which daylength influences the release of pituitary hormone that in turn regulate reproductive function. The golden hamster becomes reproductively active in the long days of summer and reproductively quiesent during winter. Natural changes in length of the light and dark portions of the day (less the 12.5h of light secretion rates of pituitary) hormones. Then, he will use drugs that affect specific chemical (neurotransmitter) systems in the brain to see if he can mimic or block the affects of daylength on hormone secretion and reproductive activity. The pineal gland, a small structure within the brain, is important in mediating the effects of daylength on reproductive function. The action of melatonin, the principal hormone of the pineal gland, on neurotransmitters and hormone secretion is not understood. He plans to study the effects of melatonin administration or removal of the pineal gland on the metabolism of brain neurotransmitters and hormone secretion. The results of these experiments should have important implications for understanding the control of reproductive function by both internal and external factors. Although he is specifically studying affects of daylength on reproductive function, the conclusions based on these studies are applicable to our understanding of how a variety of external stimuli such as food affect reproductive function.
