Perinatal neuroendocrine regulation. Development of the circadian time-keeping system

Twenty-four hour rhythms of temperature and cortisol are present in 4-day-old Cebus apella newborns.

• The biological clock in mammals, located in the suprachiasmatic nucleus (SCN), shows oscillatory function by midgestation in primates.
• Evidence suggests that maternal melatonin may entrain the fetal SCN and influence newborn circadian rhythms.
• Preliminary data indicates that exposing pregnant females to constant light inhibits maternal melatonin, altering the newborn circadian rhythms.
• Binding sites for melatonin and expression of mRNA for the Mel 1A receptor have been found in the hypothalamus, kidney, and testis.
• These findings suggest that maternal melatonin could connect the perinatal circadian time-keeping system to environmental signals.

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