Phase Delay of the Rhythm of 6-Sulphatoxy Melatonin Excretion by Artificial Light

Authors

  • D.J. Kennaway,

    Corresponding author
    1. Department of Obstetrics Gynaecology, University of Adelaide, Adelaide (D.J.K., P.F.S., P.R., F.C., H.W.) Department of Agriculture, Struan Research Centre, Struan (C.R.E.), South Australia
      Address reprint requests to D.J. Kennaway, Department of Obstetrics Gynaecology, University of Adelaide, Adelaide, South Australia 5000.
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  • C.R. Earl,

    1. Department of Obstetrics Gynaecology, University of Adelaide, Adelaide (D.J.K., P.F.S., P.R., F.C., H.W.) Department of Agriculture, Struan Research Centre, Struan (C.R.E.), South Australia
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  • P.F. Shaw,

    1. Department of Obstetrics Gynaecology, University of Adelaide, Adelaide (D.J.K., P.F.S., P.R., F.C., H.W.) Department of Agriculture, Struan Research Centre, Struan (C.R.E.), South Australia
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  • P. Royles,

    1. Department of Obstetrics Gynaecology, University of Adelaide, Adelaide (D.J.K., P.F.S., P.R., F.C., H.W.) Department of Agriculture, Struan Research Centre, Struan (C.R.E.), South Australia
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  • F. Carbone,

    1. Department of Obstetrics Gynaecology, University of Adelaide, Adelaide (D.J.K., P.F.S., P.R., F.C., H.W.) Department of Agriculture, Struan Research Centre, Struan (C.R.E.), South Australia
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  • H. Webb

    1. Department of Obstetrics Gynaecology, University of Adelaide, Adelaide (D.J.K., P.F.S., P.R., F.C., H.W.) Department of Agriculture, Struan Research Centre, Struan (C.R.E.), South Australia
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Address reprint requests to D.J. Kennaway, Department of Obstetrics Gynaecology, University of Adelaide, Adelaide, South Australia 5000.

Abstract

The purpose of this study was to investigate the effect of bright artificial light exposure on the rhythms of 6-sulphatoxy melatonin cortisol excretion in urine. Six healthy males were exposed to light (> 3,000 lux) from 1900 to 0200 h (sunset 1928 h) on one occasion. The artificial light delayed the onset of 6-sulphatoxy melatonin excretion. On the next evening the onset of 6-sulphatoxy melatonin excretion in normal light/darkness was delayed by 1 h. The timing of the peak excretion of cortisol was not affected by the light treatment; however, cortisol excretion rate was maintained at a signficantly higher rate in the morning afternoon after the treatment. These results demonstrate the inhibitory action of high intensity light in humans suggest that one 6-h period of extra light in the evening can phase delay the melatonin onset.

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