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Beyond Animal Research
By Jonathan Balcombe, Ph.D.
March 2006 |
Depressed Mice Study Is Inhumane and Clinically Irrelevant
A recent study published in the prestigious journal Science reported
on the apparent role of a protein (called p11) in fighting depression.1
However, most of the depressed subjects in this study weren’t
people—they were mice.
Some of the mice were transgenic “knockout” mice lacking
the protein in question. These mice are called “helpless” because
when they are dangled by the tail for six minutes using adhesive
tape (the “tail suspension test”) they show spontaneous
helplessness (i.e., they don’t try to right themselves as
much as mice that have the p11 protein). The study authors, who
include Nobel laureate Paul Greengard, hope the work will ultimately
lead to new depression treatments for people.
The treatment of the mice is depressing in itself. Aside from
the genetic manipulations, animals (including some rats) received
daily injections for up to four weeks, electroconvulsive treatment
delivered by ear clip electrodes, and the tail suspension test.
Killing methods involved decapitation under anesthesia, and focused
microwave irradiation, in which a powerful microwave beam is aimed
at the head of the restrained animal. Other techniques used fetal
bovine serum (acquired by inserting a large needle into the heart
of an unanesthetized fetal calf that is at least three months old
and removed from a freshly slaughtered pregnant cow) and rabbit
polyclonal antibodies (the production of which involves repeated
injections and bleedings).
Importantly, the methods include no description of the animals’ housing,
which plays an important role in the physical and psychological
welfare of rodents. Typical lab housing conditions are cramped
and barren, thwarting highly motivated natural behaviors, including
hiding, foraging, burrowing, climbing, and choosing social partners.
Some 50 percent of mice in lab cages develop stereotypic behaviors—functionless,
repetitive movements linked to the frustration of important natural
behaviors and thought to indicate psychological suffering.2
Not only is this study inhumane, it's unscientific. If we wanted
to see if something caused headaches in people, we wouldn’t
want them to be suffering headaches to begin with. It is common
for animals in laboratories to suffer from baseline depression.
How can we adequately assess “new” depression in an
already depressed animal? That mice and rats cannot verbally report
how they’re feeling is another serious drawback.
The study also found substantially lower p11 levels in human patients
with depression, which raises the question: What are we really
gaining from the mouse experiments? Because many of the procedures
done to the mice would be considered unethical in humans, not all
the findings for mice can be made for humans. But neurophysiological
and behavioral differences between people and mice make extrapolation
tenuous at best.
Jonathan Balcombe, Ph.D., is a PCRM research scientist with a background in ethology. He is the author of The Use of Animals in Higher Education, as well as many scientific papers on humane life science education and animal behavior. His recent scientific review showing that animal experiments are more stressful than previously understood was published in Contemporary Topics in Laboratory Animal Science, and a forthcoming review in Laboratory Animals reveals how laboratory housing thwarts rodents' behavioral needs. His new book, Pleasurable Kingdom: Animals and the Nature of Feeling Good, is due out in May 2006.
Literature
1. Svenningsson P, Chergui K, Rachleff I, Flajolet M, Zhang X,
El Yacoubi M, Vaugeois J-M, Nomikos GG, Greengard P. Alterations
in 5-HT1B receptor function by p11 in depression-like states. Science 2006;311:77-80.
2. Mason GJ. Stereotypies and suffering. Behavioural Processes 1991;25:103-15.
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