Pineal N-acetyltransferase activity in 10-day-old rats: A paradigm for studying the developing circadian system

Steven M. Reppert, Robert J. Coleman, Harley W. Heath, Jason R. Swedlow

    Research output: Contribution to journalArticlepeer-review

    72 Citations (Scopus)


    Pineal N-acetyltransferase (NAT) activity in 10-day-old rat pups was used to examine several aspects of the developing circadian timing system. When born and reared under constant darkness, 10-day-old animals manifested a clear daily rhythm of NAT activity whose phase was in time with the estimated circadian time of the mother (set by the lighting cycle during pregnancy). When pups were reared in constant darkness from birth by a foster mother whose circadian time was 180° (12 h) out of phase with that of the natural mother, the resulting population profiles of NAT activity were arrhythmic. Analysis of the individual litter profiles from this experiment showed a variable postnatal influence of the maternal circadian system on the timing of the developing circadian system. Neither cross-fostering per se nor social interactions among litter mates contributed significantly to the apparent maternal influence. The magnitude of the postnatal maternal influence was not the same throughout development, but was most apparent during the first 5 days of life. Neonatal blinding (within 24 h of birth) did not appreciably alter the maternal influence. Extraretinal photore-ception does not contribute to entrainment of the circadian clock during postnatal development, and retina-mediated photic entrainmerit is present by 10 days of age. The results indicate that pineal NAT activity monitored in 10-day-old rats provides a useful paradigm for studying the developing circadian system.

    Original languageEnglish
    Pages (from-to)918-925
    Number of pages8
    Issue number3
    Publication statusPublished - 1 Sept 1984

    ASJC Scopus subject areas

    • Endocrinology


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