Effects of indirect light and propranolol on melatonin levels in normal human subjects

Aimee Mayeda, Stuart Mannon, John Hofstetter, Melody Adkins, Reba Baker, Kuolung Hu, John Nurnberger

Research output: Contribution to journalArticle

13 Scopus citations


An indirect lighting protocol was developed to measure nocturnal melatonin suppression by light in normal human subjects. Goals were to minimize both discomfort due to staring intensely at a bright light source, and behavioral variation due to wandering gaze. Subjects sat with a bank of five full-spectrum light sources placed behind them. Lights reflecting off the surfaces before each subject produced a hemisphere of light that measured 500 lx ± 5%. Subjects retired to bed in darkness by midnight and then sat in the hemisphere of light from 02.00 h to 04.00 h. Blood for melatonin was drawn at 20-30-min intervals from midnight to 06.00 h. Plasma melatonin was measured by radioimmunoassay. The indirect lighting protocol was used to compare the effects of 500 lx light to dark (21 subjects) and to study varying light intensities from 300 to 2000 lx (7 subjects). We studied the effects of the sitting posture in very dim light of 20-30 lx (6 subjects). We also studied the effects of propranolol plus dark and propranolol plus 500 lx light on melatonin levels. Subjects received placebo, 10 mg propranolol or 40 mg propranolol orally at 23.00 h, and were then exposed to either the dark or light condition. Melatonin levels obtained with the indirect lighting protocol were consistent with studies using direct lighting; light of 500 lx significantly suppressed nocturnal melatonin and suppression was dose related between 300 and 2000 lx. Sitting in dim light had no significant effect on melatonin suppression when compared with the supine posture in the dark in six subjects. Propranolol caused a dose-dependent decrease in melatonin levels in both the dark and the light. There was no relationship between suppression of melatonin by propranolol and suppression by light.

Original languageEnglish (US)
Pages (from-to)9-17
Number of pages9
JournalPsychiatry Research
Issue number1
StatePublished - Oct 19 1998


  • Human
  • Light
  • Melatonin
  • Propranolol

ASJC Scopus subject areas

  • Psychiatry and Mental health
  • Biological Psychiatry
  • Psychology(all)

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