A new study is wafting an odor of uncertainty over the results of prior experiments using lab rats and mice. Researchers have discovered that the scent of a human male significantly stresses the critters, an effect not seen in response to females.
Researchers from McGill University in Montreal discovered that, in the presence of men, mice display a stress response equivalent to being placed in a confined space, such as a tube, for 15 minutes. The study is the first to systematically test this aspect of rodents’ response to their handlers.
“Scientists whisper to each other at conferences that their rodent research subjects appear to be aware of their presence, and that this might affect the results of experiments, but this has never been directly demonstrated until now,” Jeffrey Mogil, a psychology professor at McGill who led the study, said in a statement.
A Frightening Odor
The research team administered pain-inducing injections to mice and rats and monitored their facial grimaces, which is a measure of pain. When rodents are stressed, they grimace less, because their fight-or-flight response kicks in and mitigates discomfort. When a man was in the room, the rodents grimaced 35 percent less than when no one was in the room. However, there was no significant difference if a female was sitting in the room.
To determine if rodents were reacting to scent and not something else, researchers placed T-shirts worn by either men and women in the cage with them. The critters showed the same gender-specific response. Further, they showed the same response when exposed to bedding used by male cats and dogs, as well as to synthetic versions of chemicals secreted from mens’ armpits.
“Our data suggest instead that an odor evoked by a cocktail of chemicals within the body secretions of isolated males (except cage mates) produce stress in rodents,” researchers wrote in their report, published Monday in the journal Nature Methods.
Producing replicable results is the standard that scientists strive for in their published studies. However the new study indicates that lab animals’ biology and behavior might be affected not just by the experimental treatment but by the experimenters themselves.
How the discovery is translated into better experimental methods is far from clear at this point. Still, Mogil told TheStar.com, “This is a finding that’s going to make scientific research better, more reliable than it’s been before.”
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