Maternal endocrine extirpations do not abolish maternal coordination of the fetal circadian clock.

The maternal circadian system coordinates the timing of the fetal circadian clock to the prevailing light-dark cycle. The role of various maternal endocrine organs as the source of a coordinating signal was investigated in rats. Either metabolic activity of the fetal suprachiasmatic nuclei or pineal N-acetyltransferase activity in 10-day-old pups was used to monitor the fetal circadian clock. Extirpations of the maternal pituitary, adrenals, thyroid-parathyroids, ovaries, or pineal (each performed in separate experiments) did not abolish maternal coordination.