Bioscientifica Proceedings

We have investigated whether the maternal melatonin rhythm provides the fetus with either a circadian or seasonal ‘signal’ during development. Our findings provide evidence that melatonin can generate and entrain the early evening peak in the daily rhythm of fetal breathing movements. In contrast, daily variations in maternal and fetal prolactin concentrations are present in pinealectomized ewes, are altered by changes in the time of onset of darkness, but are unal...