Daily cycle and development of arg-vasopressin levels in the brain's body clock area of young rats

AVP levels in the rat pup suprachiasmatic nucleus increased from postnatal day 1, reaching adult levels by postnatal days 10-12.

• AVP content demonstrates a marked increase over the early postnatal period.
• A diurnal rhythm similar to that of adults appears at postnatal days 10-12 under light-dark cycle conditions.
• The peak AVP levels are observed during the early light period, while the lowest levels occur at the end of the light period.
• Circadian rhythms of AVP persist for 7 days under constant dark or constant light conditions.
• Oscillation of AVP levels begins after postnatal day 10-12, indicating a developing rhythmicity during the nursing phase.

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