Deciphering the Function of the Blunt Circadian Rhythm of Melatonin in the Newborn Lamb: Impact on Adrenal and Heart

Daily oral doses of melatonin (0.25 mg/kg) given to newborn lambs suppressed clock time-related changes in hormonal and gene expression markers.

• Newborn lambs typically have low levels of melatonin until around 2 weeks of life.
• Maternal melatonin transfer during pregnancy is important for newborn physiological adjustments.
• Imposing a melatonin rhythm in newborn lambs affected cortisol levels and gene expression in the adrenal gland.
• Melatonin treatment led to a decrease in the heart/body weight ratio and altered heart gene expression compared to controls.
• The findings suggest that the absence of a melatonin rhythm may play a significant role in neonatal adaptation.

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