Mechanisms of Maternal Transfer of Photoperiodic Information

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Changes in hormone levels and metabolism in pregnant females in a number of species, including humans, can influence the development of the fetus. These changes in fetal development can result from adaptive responses to normal fluctuations in the environment as well as from the teratogenic effects of chemicals injected by the mother. Indeed the toxic effects of nicotine, cocaine and alcohol result from their interference with the normal biochemical pathways that regulate fetal development, pathways similar to those used in an organism's normal adaptive response. Dr. Horton will examine the mechanisms by which the maternal system transmits information about changes in day length, a naturally occurring environmental cue, to the fetus during gestation. It is known that prenatal photoperiodic information influences postnatal rate of growth, body weight and reproductive development. She proposes that melatonin, a hormone produced and secreted by the pineal gland, is a likely candidate for this transfer of information since it crosses the placenta from the maternal to the fetal circulation and is involved in regulation of circadian rhythmicity. Using an innovative technical procedure to administer melatonin in a physiologically meaningful manner, Dr. Horton will identify those factors in the maternal system which communicate day length information to the fetus. The results of these fundamental studies will lead to a better understanding of the mechanism by which the maternal system can alter the unfolding intrinsic genetic program regulating the development of the fetus.