Melatonin: A universal time messenger

Thomas C. Erren, Russel J. Reiter

Research output: Contribution to journalReview articlepeer-review

29 Scopus citations


Temporal organization plays a key role in humans, and presumably all species on Earth. A core building block of the chronobiological architecture is the master clock, located in the suprachi asmatic nuclei [SCN], which organizes "when" things happen in sub-cellular biochemistry, cells, organs and organisms, including humans. Conceptually, time messenging should follow a 5 step-cascade. While abundant evidence suggests how steps 1 through 4 work, step 5 of "how is central time information transmitted througout the body?" awaits elucidation. Step 1: Light provides information on environmental (external) time; Step 2: Ocular interfaces between light and biological (internal) time are intrinsically photosensitive retinal ganglion cells [ipRGS] and rods and cones; Step 3: Via the retinohypothalamic tract external time information reaches the light-dependent master clock in the brain, viz the SCN; Step 4: The SCN translate environmental time information into biological time and distribute this information to numerous brain structures via a melanopsin-based network. Step 5: Melatonin, we propose, transmits, or is a messenger of, internal time information to all parts of the body to allow temporal organization which is orchestrated by the SCN. Key reasons why we expect melatonin to have such role include: First, melatonin, as the chemical expression of darkness, is centrally involved in time- and timing-related processes such as encoding clock and calendar information in the brain; Second, melatonin travels throughout the body without limits and is thus a ubiquitous molecule. The chemial conservation of melatonin in all tested species could make this molecule a candidate for a universal time messenger, possibly constituting a legacy of an all-embracing evolutionary history.

Original languageEnglish (US)
Pages (from-to)187-192
Number of pages6
JournalNeuroendocrinology Letters
Issue number3
StatePublished - 2015
Externally publishedYes


  • Calendar
  • Clock
  • Evolution
  • IpRGC
  • Melanopsin-based network
  • Melatonin
  • SCN
  • Temporal organization
  • Time messenger
  • Time provider

ASJC Scopus subject areas

  • Endocrine and Autonomic Systems
  • Clinical Neurology
  • Neurology
  • Psychiatry and Mental health
  • Endocrinology
  • Endocrinology, Diabetes and Metabolism


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