Apr. 18,
2013 — When faced with impossible circumstances beyond their control, animals,
including humans, often hunker down as they develop sleep or eating disorders,
ulcers, and other physical manifestations of depression. Now, researchers
reporting in the Cell Press journal Current Biology on April 18 show
that the same kind of thing happens to flies.
The study is a
step toward understanding the biological basis for depression and presents a
new way for testing antidepressant drugs, the researchers say. The discovery of
such symptoms in an insect shows that the roots of depression are very deep
indeed.
"Depressions
are so devastating because they go back to such a basic property of
behavior," says Martin Heisenberg of the Rudolf
Virchow Center
in Würzburg , Germany .
Heisenberg
says that the idea for the study came out of a lengthy discussion with a
colleague about how to ask whether flies can feel fear. Franco Bertolucci, a
coauthor on the study, had found that flies can rapidly learn to suppress
innate behaviors, a phenomenon that is part of learned helplessness.
The
researchers now show that flies experiencing uncomfortable levels of heat will
walk to escape it. But if the flies realize that the heat is beyond their
control and can't be avoided, they will stop responding, walking more slowly
and taking longer and more frequent rests, as if they were
"depressed."
Intriguingly,
female flies slow down more under those stressful circumstances than males do.
It's not clear exactly what that means, but Heisenberg explains, "if we
realize that the fly trapped in a strange, dark box, unable to get rid of the
dangerous heat pulses, has to find a compromise between saving energy and not
missing any chance of escape, we can understand that such a compromise may come
out differently for males and females, as their resources and goals in life are
different."
Heisenberg's
team now intends to explore other questions, such as: How long does the flies'
depression-like state last? How does it affect other behaviors, like courtship
and aggression? What is happening in their brain? And more.
Heisenberg
says that the findings are a reminder of a lesson that children's books are
often best at showing: "Animals have lots in common with us humans. They
breathe the same air, share many of the same resources, actively explore space,
and have distinct social roles. Their brains serve the same purpose, too: they
help them to do the right thing."
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