REC -
I had to check to see if the date was April 1 instead of May 1... is
this an off-by-one error in your calendar?
And do they *really* use a "grimace scale" to measure the pain inflicted
in mice by injecting (what... lye?) into their feet? Geeze... Are you
sure this wasn't published on April 1? Throw in a cardboard cutout of
Paris Hilton for comic relief!
Any lab rat or woman could have told you "men stink". No need for an
elaborate study!
-RUIN
http://www.sciencemag.org/content/344/6183/461.full
Male Scent May Compromise Biomedical Studies
1. David Grimm
<http://www.sciencemag.org/search?author1=David+Grimm&sortspec=date&submit=Submit>
Jeffrey Mogil's students suspected there was something fishy going on
with their experiments. They were injecting an irritant into the feet
of mice to test their pain response, but the rodents didn't seem to
feel anything. "We thought there was something wrong with the
injection," says Mogil, a neuroscientist at McGill University in
Montreal, Canada.
The real culprit was far more surprising: The mice that didn't show
pain had been handled by /male/ students. Mogil's group discovered
that this gender distinction alone was enough to throw off their whole
experiment---and likely influences the work of other researchers as well.
"This is very important work with wide-ranging implications," says M.
Catherine Bushnell, a neuroscientist and the scientific director of
the Division of Intramural Research at the National Center for
Complementary and Alternative Medicine (NCCAM) in Bethesda, Maryland.
"Many people doing research have never thought of this."
Mogil has studied pain for 25 years. He's long suspected that lab
animals respond differently to the sensation when researchers are
present. In 2007, his lab observed that mice spend less time licking a
painful injection---a sign that they're hurting---when a person is
nearby, even if that "person" is a cardboard cutout of Paris Hilton.
Other scientists began to wonder if their own data were biased by the
same effect. "There were whisperings at meetings that this was
confounding research results," Mogil says.
So he decided to take a closer look. In the new study, Mogil told the
researchers in his lab to inject an inflammatory agent into the foot
of a rat or mouse and then take a seat nearby and read a book. A video
camera trained on the rodent's face assessed the animal's pain level,
based on a 0- to 2-point "grimace scale" developed by the team. The
results were mixed. Sometimes the animals showed pain when an
experimenter was present, and sometimes they seemed just fine. So, on
a hunch, Mogil and colleagues recrunched the data, this time
controlling for whether a male or a female experimenter was present.
"We were stunned by the results," he says. The rodents showed
significantly fewer signs of pain (an average of a 36% lower score on
the grimace scale) when a male researcher was in the room than when a
female researcher---or no researcher at all---was there.
Thinking back to his Paris Hilton experiment, Mogil wondered whether
the rodents were responding to the sight of a woman or man or to
something more subtle. So he told the people in his lab to place their
worn T-shirts near injected animals and then leave the room. Even when
the humans weren't present, the results were the same. Rats and mice
showed about a 36% lower score on the grimace scale when exposed to
male versus female T-shirts, the team reported online this week in
/Nature Methods./ (Female mice were slightly more sensitive to the
effect.) Placing a woman's T-shirt next to a man's T-shirt negated the
impact. Bedding material from unfamiliar male mice and guinea pigs, as
well as pet beds slept in by unsterilized male cats and dogs, produced
the same response: Male odors seemed to act like painkillers.
Further testing showed that the rodents exposed to male odors were
actually feeling less pain, rather than simply hiding the pain they
were in. The male aroma ramped up their stress levels, which deadened
the hurt. "It's really astounding that such a robust effect could have
been missed for so many years," Mogil says.
He suspects the rodents are reacting to scent chemicals that male
mammals have produced for eons. "It's a primordial response," he says.
"If you smell a solitary male nearby, chances are he's hunting or
defending his territory." If you're in pain, you're showing weakness.
Almost every animal behavior studied in the lab, from the
effectiveness of experimental drugs to the ability of monkeys to do
math, is affected by stress, notes Paul Flecknell, a veterinary
anesthesiologist at Newcastle University in the United Kingdom who
researches ways to alleviate pain in animals. "This could have an
impact on just about everything."
Male odor could even influence human clinical trials. If a male doctor
injects you with a new kind of pain medication, do you feel better
because of the drug---or because of his gender? "It's not an
unreasonable concern," Flecknell says.
The findings may also suggest why some labs have trouble reproducing
the results of other groups. "Sometimes pharmaceutical companies can't
replicate preclinical work," says Bushnell, who came to NCCAM to
develop a pain research program. "This could help explain that."
Still, Mogil doesn't think scientists need to redo decades of animal
research. "It's a confounding factor, but not a fatal one," he says.
But going forward, he advises, researchers should pay more attention
not to just what experiments they're doing, but also to who's doing
the experiments. "I joke that the solution is to fire all the male
researchers," Mogil says. "But at the very least, this is something
teams should be noting in the methods sections of their papers. We can
change the bath water without throwing out the baby."
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