Circadian Melatonin - Learning Objectives

• What is melatonin and what does it do?
• How is and when is melatonin made?
• What is seratonin and what is it for?
• ​How are melatonin and serotonin related?​
• What is synthetic melatonin?

The sun plays an important role in our wake and sleep cycles, known as your Circadian Rhythm.

Our ancestors evolved under the natural cycles of day-light and dark -night. Light is energy that influences mind and body - many chemicals in our bodies are controlled by light.  ​

Melatonin

Melatonin is produced at night to direct our bodies to sleep. Exposure to blue tinted light can delay sleep for as much as two hours.

“Most of the effects of a light exposure comes within the first few minutes.” Shadab Rahman - Meeting the Moment: Lighting and Wellness, IES Webinar 06-03-21 
https://sleep.hms.harvard.edu/faculty-staff/shadab-rahman

Characterizing the temporal Dynamics of Melatonin and Cortisol Changes in Response to Nocturnal Light Exposure.
Authors: Authors: Rahman SA, Wright KP, Lockley SW, Czeisler CA, Gronfier C.
Sci Rep 2019-12-23
View full abstract on Pubmed https://pubmed.ncbi.nlm.nih.gov/31873098/
Twenty-one young healthy participants were randomized to receive either intermittent bright (~9,500 lux) light (IBL), continuous bright light (CBL) or continuous dim (~1 lux) light (VDL) for 6.5 h during the biological night (n = 7 per condition). Melatonin suppression occurred rapidly within the first 5 min and continued until the end of each IBL stimuli (t1/2 = ~13 min). Melatonin recovery occurred more slowly between IBL stimuli (half-maximal recovery rate of ~46 min). Mean melatonin suppression (~40%) and recovery (~50%) were similar across IBL stimuli.  [1]

Melatonin levels. The change in season can disrupt the balance of the body's level of melatonin, which plays a role in sleep patterns and mood." [2]

Serotonin

Serotonin levels. A drop in serotonin, a brain chemical (neurotransmitter) that affects mood, might play a role in SAD. Reduced sunlight can cause a drop in serotonin that may trigger depression. SAD

Its biological function is complex and multifaceted, modulating mood, cognition, reward, learning, memory, and numerous physiological processes such as vomiting and vasoconstriction [3]

Circadian System

Photo receptors in your eyes include Rods, Cones, and Ganglion Cells.  Photobiologists and Circadian System Researchers explain how light affects human biology and trends in Circadian Adjusted lighting.
https://www.youtube.com/watch?v=ZrKkzm2HQAo

This Biological Clock diagram represents the natural circadian rhythm of a human day and night.

"A circadian rhythm /sɜːrˈkeɪdiən/ is any biological process that displays an endogenous, entrainable oscillation of about 24 hours. These 24-hour rhythms are driven by a circadian clock, and they have been widely observed in plants, animals, fungi, and cyanobacteria." [4]

Animals & Plants Circadian Clocks

 Animals and plants also have natural Circadian clocks regulating growth and biological processes.

Animals exposed to light pollution will delay their foraging and hunting for several hours after dark, and wait until they have extreme hunger, to begin searching for food. This disruption in their natural cycles creates an imbalance in their biological systems.

One study showed that fish would not swim under a bridge brightly lit with blue lighting at night.

Many animals grow warmer coats in winter, their fur coats stimulated to grow by the shorter daylight hours with the coming of winter, not the chilling temperatures.

While certain ecological problems associated with artificial night lighting are widely known-for instance, the disorientation of sea turtle hatchlings by beachfront lighting-the vast range of influences on all types of animals and plants is only beginning to be recognized. From nest choice and breeding success of birds to behavioral and physiological changes in salamanders, many organisms are seriously affected by human alterations in natural patterns of light and dark.

Ecological Consequences of Artificial Night Lighting is the first book to consider the environmental effects of the intentional illumination of the night. It brings together leading scientists from around the world to review the state of knowledge on the subject and to describe specific effects that have been observed across a full range of taxonomic groups, including mammals, birds, reptiles and amphibians, fishes, invertebrates, and plants.

For more information read the book Ecological Consequences of Artificial Night Lighting By Catherine Rich and Travis Longcore. [5]

2017 Nobel Prize for Circadian Rhythm Research

The circadian clock anticipates and adapts our physiology to the different phases of the day.  Our biological clock helps to regulate sleep patterns, feeding behavior, hormone release, blood pressure, and body temperature.

The Nobel Prize in Physiology or Medicine 2017, for their discoveries of molecular mechanisms controlling the circadian rhythm
Jeffrey C. Hall, Michael Rosbash, Michael W. Young [6]

Circadian Brain

Brain Signals

The controller of our Circadian System producing Melatonin is the Pineal Gland, this part of the Endocrine System, sometimes referred to as the 'third eye' is located deep inside our brain, directly above the optic chiasm. . It receives signals though our eyes, collecting information about light intensity and color via the optic nerves.  "Suprachiasmatic nuclei (SCN), located in the hypothalamus above the optic chiasm."

Hormones - Melatonin and Serotonin, are created in our bodies to signal us to sleep and wake.

Cyto-architecture is a biology term used to describe the study of the arrangement of cells and how this affects the performance of each organ. Often referred to as study of the brain structure, 'cyto' means 'cells' and 'architecture' originates from Greek arkhitekton 'master builder.' Studying the architecture of the brain,  is analogous to the study of buildings, their manner of construction and the arrangement of their parts. As recently as 2002 scientists discovered photoreceptors called ganglion cells (RGC) in our eye's retina that respond to light and send signals to our circadian system.  Scientists continue to search for understanding of the brain circuits, receptors, and their functions. [7]

---

Circadian Response Curve
Blue light will keep you awake.

Use amber or red night lights.
Circadian rhythm sleep disorders, such as jet lag syndrome and shift work sleep disorder, are those specifically attributed to dysfunctions or insufficiencies in the circadian system. Taking into consideration the preeminence of the circadian clock in timing sleep, it is likely that other sleep disorders, such as insomnia, are also linked to circadian system abnormalities. [8]

Quantifying Circadian Light and Its Impact

February 13, 2017 article featured in Architectural Lighting Magazine
http://www.archlighting.com/technology/quantifying-circadian-light-and-its-impact_o
Melanopic lux is the wrong metric for describing circadian-effective light. Here is a better alternative. By Mariana Figueiro, Mark Rea 

• Mariana Figueiro, FIES, is a professor at the Lighting Research Center at Rensselaer Polytechnic Institute, where she also directs the Light and Health program.
• Mark Rea, FSLL, is a professor at the Lighting Research Center and has served as its director since its founding in 1988.

---

Footnotes

1. Rahman SA, Wright KP, Lockley SW, Czeisler CA, Gronfier C. Characterizing the temporal Dynamics of Melatonin and Cortisol Changes in Response to Nocturnal Light Exposure.  Sci Rep 2019-12-23  View full abstract on Pubmed https://pubmed.ncbi.nlm.nih.gov/31873098/
2. ​Mayo Clinic, Seasonal affective disorder (SAD)
3. Young SN (November 2007). "How to increase serotonin in the human brain without drugs". Journal of Psychiatry & Neuroscience. 32 (6): 394–9. PMC 2077351. PMID 18043762 Wikipedia
4. Mark Rea, Director of the Lighting Research Center (LRC) and Professor of Architecture and Cognitive Sciences at Rensselaer Polytechnic Institute. Presentation Lightfair 2006 Current standards described in Lighting for Today's Neonatal Intensive Care Unit. 2010 http://www.sciencedirect.com/science/article/pii/S1527336910000322
5. Circadian Rhythms in Humans, Animals, & Plants. https://islandpress.org/book/ecological-consequences-of-artificial-night-lighting?utm_source=Light+Pollution+and+islandpress.org/book/ecological-consequences-of-artificial-night-lighting?utm_source=Light+Pollution+and+the+Ecological+Consequences+of+Artificial+Night&
6. "The 2017 Nobel Prize in Physiology or Medicine - Press Release". Nobelprize.org. Nobel Media AB 2014. Web. 14 Nov 2017. <http://www.nobelprize.org/nobel_prizes/medicine/laureates/2017/press.html>
7. Brown University, Department of Neuroscience    https://neuroscience.brown.edu/Berson/research.html
8. The human circadian system in normal and disordered sleep.  http://www.ncbi.nlm.nih.gov/pubmed/16336035

Photo Credits

Human Biological Clock - Wiki
Circadian Brain - CTC - http://braintreatmentcenter.com/

Circadian Clock© The Nobel Committee for Physiology or Medicine. Illustrator: Mattias Karlén.

Related Topics

Light Therapy Topics, Nightlights, Sleep, Blue Dimming Apps, Ecology of Night Lighting, Dark Sky, SAD, Circadian Ganglion, Circadian Explained