Scientists show how light therapy treats depression in mice model
Light activates the circadian clock gene Period1 in a brain region that affects the mood

Date:
July 8, 2021
Source:
PLOS
Summary:
Light therapy can help improve the mood of people with seasonal
affective disorder (SAD) during short winter days, but exactly
how this therapy works is not well understood. A new study finds
that light therapy's beneficial effects come from activating the
circadian clock gene Period1 in a part of the brain involved in
mood and sleep-wake cycles.



FULL STORY ========================================================================== Light therapy can help improve the mood of people with seasonal
affective disorder (SAD) during short winter days, but exactly how this
therapy works is not well understood. A new study by Urs Albrecht at the University of Fribourg, published July 8th in the journal PLOS Genetics,
finds that light therapy's beneficial effects come from activating the circadian clock gene Period1 in a part of the brain involved in mood
and sleep-wake cycles.


========================================================================== Nighttime light has strong effects on the physiology and behavior
of mammals.

It can reset an animal's circadian rhythms, and in the form of light
therapy, affect mood in humans. Albrecht and his colleagues investigated
how nighttime light impacts mood using mice as a model. They exposed
mice to a pulse of light at different points during the night and
then tested them for depressive behavior. The researchers discovered
that light exposure at the end of the dark period -- two hours before
daytime -- had an antidepressant effect on the animals. The pulse of
light activated the Period1 gene in a brain region called the lateral
habenula, which plays a role in mood. Light at other times, however,
had no effect. When they deleted the Period1 gene, the mice no longer experienced the light's beneficial effects.

The new results provide evidence that turning on Period1 in the lateral habenula is the key to light's mood-boosting powers. The discovery that
mice appeared to be less depressed when exposed to light at the end of the
dark period than the beginning is similar to findings in humans. Light
therapy is more efficient in the early morning than in the evening for
patients with SAD.

However, the researchers caution against making too many direct
comparisons to humans since mice are nocturnal animals.

The researchers add, "Light perceived in the late part of
the night induces expression of the clock gene Per1, which
is related to improvement of depression like behavior in mice." ========================================================================== Story Source: Materials provided by PLOS. Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. Iwona Olejniczak, Ju"rgen A. Ripperger, Federica Sandrelli,
Anna Schnell,
Laureen Mansencal-Strittmatter, Katrin Wendrich, Ka Yi Hui, Andrea
Brenna, Naila Ben Fredj, Urs Albrecht. Light affects behavioral
despair involving the clock gene Period 1. PLOS Genetics, 2021;
17 (7): e1009625 DOI: 10.1371/journal.pgen.1009625 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/07/210708143918.htm

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