Human melatonin suppression by light: a case for scotopic efficiency

Neurosci Lett. 2001 Feb 16;299(1-2):45-8. doi: 10.1016/s0304-3940(01)01512-9.


Human adult males were exposed to combinations of two illuminances and two spectral power distributions over the course of four nighttime sessions. A dose-dependent response of acute melatonin suppression to light was found, but photopic (cone-based) illuminance did not adequately predict suppression. When melatonin suppression was plotted against scotopic (rod-based) illuminance, the data formed a nearly monotonic function, implicating rods, or a rod-dominated mechanism, in the human melatonin regulation system. The results do not, however, rule out mechanisms other than rods, including novel photoreceptors, as candidates for melatonin regulation in humans.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Circadian Rhythm / physiology*
  • Dark Adaptation / physiology
  • Darkness*
  • Humans
  • Light Signal Transduction / physiology*
  • Light*
  • Male
  • Melatonin / blood
  • Melatonin / metabolism*
  • Middle Aged
  • Photic Stimulation / methods
  • Pineal Gland / metabolism
  • Radioimmunoassay
  • Retinal Cone Photoreceptor Cells / physiology
  • Retinal Rod Photoreceptor Cells / physiology*


  • Melatonin