'Second-hand' psychological stress can lead to depression in mice, finds
study

Date:
September 22, 2021
Source:
Tokyo University of Science
Summary:
Few studies have explored the effect of psychological stressors
on behavior, and neurogenesis, in the context of depression. With
the elucidation of a vicarious social defeat stress mouse model,
scientists have successfully endeavored in connecting the dots
between psychological stress and depression.



FULL STORY ========================================================================== Depression is a serious medical condition that plagues modern
society. Several theories have been proposed to explain the physiological
basis of depression, of which the "neurogenic hypothesis of depression"
has garnered much attention.

The theory follows that deterioration in brain regions, like hippocampus,
can result in depression. This deterioration can be caused by physical
and psychological stress. While the depressive effects of physical stress
have been well studied, little is known about psychological stress in
this regard.


========================================================================== Recent research has explained how vicarious social defeat can
cause psychological stress in mice. This involves the mouse being
made to experience defeat of another mouse in an experimental social
setting. Using this model, a group of scientists from Japan attempted to establish a link between depressive symptoms and hippocampal neurogenesis.

Prof. Akiyoshi Saitoh from Tokyo University of Science, one of the
lead authors of the study, further explains the motivation behind this research, "The number of individuals suffering from depression has been
on the rise the world over.

However, the detailed pathophysiology of depression still remains to
be elucidated. So, we decided to focus on the possible mechanism of psychological stress in adult hippocampal neurogenesis, to understand
its role in depressive disorders." The study was published in the journal Behavioural Brain Research.

After exposing the mice to chronic vicarious social defeat stress,
Prof. Saitoh and the team, including Mr. Toshinori Yoshioka and
Dr. Daisuke Yamada from Tokyo University of Science, analyzed their
behavior and brains in close detail. Aside from behavioral deficits like
social withdrawal, the stressed mice also showed a significant decrease
in the survival rate of new-born neurons in the dentate gyrus, a region in
the hippocampus responsible for sensory perception and memory, compared to
the non-stressed controls. This condition persisted for up to four weeks,
after "stressing" the mice. However, cell growth, differentiation, and maturation did not differ between the groups of mice during the period of observation. Notably, the cell survival rate was restored in the stressed
mice after treatment with a chronic antidepressant called fluoxetine.

Regarding the results, Mr. Toshinori Yoshioka adds, "We have found out
that chronic mental stress affects the neurogenesis of the hippocampal
dentate gyrus. Also, we believe that this animal model will play an
important role in elucidating the pathophysiology of depression, and in
the development of corresponding novel drug." Overall, this study has
provided important insights into the pathophysiology of depression. Also,
it goes without saying how this study paves the way for future research
into the role of psychological stress in depression.

========================================================================== Story Source: Materials provided by Tokyo_University_of_Science. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Toshinori Yoshioka, Daisuke Yamada, Riho Kobayashi, Eri
Segi-Nishida,
Akiyoshi Saitoh. Chronic vicarious social defeat stress attenuates
new- born neuronal cell survival in mouse hippocampus. Behavioural
Brain Research, 2022; 416: 113536 DOI: 10.1016/j.bbr.2021.113536 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/09/210922121859.htm

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