Summary
This conceptual paper proposes that melatonin serves as a universal internal time messenger, transmitting SCN-derived circadian information to all tissues and organs via the bloodstream. For lighting designers and healthcare practitioners, this reinforces that controlling light exposure—particularly its timing and spectral composition—is critical for regulating melatonin secretion and thereby the body's entire temporal organization.
Key Findings
- The authors propose a 5-step cascade for circadian time-keeping: (1) light provides external time cues, (2) ipRGCs, rods, and cones serve as ocular interfaces, (3) the retinohypothalamic tract conveys signals to the SCN, (4) the SCN distributes time information via a melanopsin-based network, and (5) melatonin transmits this internal time information throughout the body.
- Melatonin is described as the 'chemical expression of darkness,' encoding both clock (time of day) and calendar (time of year) information and traveling ubiquitously throughout the body without apparent physiological barriers.
- The chemical conservation of melatonin across all tested species is cited as evidence for its role as a universal time messenger with deep evolutionary origins.
Categories
Sleep & Circadian Health: Melatonin's role as a chemical messenger of darkness is central to circadian rhythm entrainment and temporal organization throughout the body.
The Science of Light: The paper details the 5-step cascade from light detection by ipRGCs and rods/cones through the retinohypothalamic tract to the SCN, explaining the photobiological basis of circadian time-keeping.
Author(s)
TC Erren, RJ Reiter
Publication Year
2015
Number of Citations
61
Related Publications
Sleep & Circadian Health
- Phototransduction by retinal ganglion cells that set the circadian clock
- The mammalian circadian timing system: organization and coordination of central and peripheral clocks
- The two‐process model of sleep regulation: a reappraisal
- Melanopsin is required for non-image-forming photic responses in blind mice
- Strange vision: ganglion cells as circadian photoreceptors
The Science of Light
- Phototransduction by retinal ganglion cells that set the circadian clock
- Color appearance models
- The mammalian circadian timing system: organization and coordination of central and peripheral clocks
- Diminished pupillary light reflex at high irradiances in melanopsin-knockout mice
- Melanopsin is required for non-image-forming photic responses in blind mice