Periodic absence of nursing mothers phase‐shifts circadian rhythms of clock genes in the suprachiasmatic nucleus of rat pups

Periodic maternal deprivation during the first week of life completely phase-reversed circadian rhythms in neonatal rats.

• The absence of nursing mothers altered the expression rhythms of the clock genes rPer1 and rPer2 in the pups' brain regions associated with circadian regulation.
• Spontaneous locomotor activity in the pups was also affected after weaning at postnatal day 21.
• Stress-related gene expressions, including corticotropine-releasing hormone, arginine vasopressin, and glucocorticoid receptor, were modified in the mother-deprived pups.
• These changes occurred specifically in certain brain areas of the pups by postnatal day 6.
• The findings suggest that maternal absence may reset the neonatal circadian clock and influence stress responses.

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