Male Researchers Stress Out Rodents

http://www.scientificamerican.com/article/male-researchers-stress-out-rodents/

Apr 28, 2014 |By Alla Katsnelson

Male, but not female, experimenters induce intense stress in rodents that can dampen pain responses, according to a paper published today in Nature Methods. Such reactions affect the rodents’ behaviour and potentially confound the results of animal studies, the study suggests.

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It wasn’t just men who caused the stress spike in the rodents, but any nearby male animal, including guinea pigs, rats, cats and dogs. Male cage-mates of the animal being tested were the only exception, and produced no changes in stress hormone levels.

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More than just a curiosity, this stress response can throw a curveball into study results. On reanalysing data from the group’s past studies, such as on pain sensitivity to hot water, the researchers found that mice tested by men showed lower baseline pain sensitivity than mice tested by women.The work indirectly demonstrates potential effects on nearly any kind of medical research, says Joseph Garner, who studies mouse behavior and well-being at Stanford University in California.

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Animal researchers, says Garner, will have to embrace statistical methods that compensate for a greater range of variability. “We need to think about animals as more like human subjects,” he says, “than as controllable reagents.”