Lab Mice Are So Stressed Out By Male Researchers, They Suppress Their Pain Response To Them

By Gabrielle Jonas on April 29, 2014 3:16 PM EDT

schankz  http://www.shutterstock.com/pic-157982033/stock-photo-head-mouse-macro.html?src=M2J0Qh-duft_GU70Vtdm-g-1-5

A study finding that lab mice are so fearful of male handlers that they suppress their pain response to them may have implications for other science research. The study, which appeared in Nature Methods Monday, indicates that when lab mice and rats are given painful stimuli in the presence of men, they show and feel show the pain worse than when a female is present.

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The rodents were given pain stimuli through injections of inflammatories to two of their ankles and their reactions were guaged by measuring the degree to which they grimaced in pain in the presence of men, women, and no observor. When a male was sitting about 20 inches (0.5 meters) away from them while the injection was administered, they grimaced about 36 percent less than when no one or a female was there. Female rats had an even more intense reaction to male observors. Surprisingly, there was no signficiant difference guaged in the reactions of the rodents to the gender of the person administering the injections. The researchers verified the fact that the rodents' olifactory senses were at play by being able to replicate this effect with T-shirts worn by men, bedding material from unfamiliar male mammals who are not secreting smells from their gonads, and presentation of compounds secreted from the human armpit.  They didn't respond with less show of pain to smells from their cage-mates, either. 

The researchers also tested to what degree the rodents secreted opiates from their brains in the presence of males as opposed to females, and found that they secreted far more opiates to block pain than when in the presence of females or no one at all. In addition,they revisited past studies from their laboratory at McGill University involving rodents, noting that the baseline pain reaction varied between whether female or male lab personnel were present when they were being administered painful stimuli, suggesting that results could have been inadvertently skewed.

"The solution is simply to report the gender of the experimenter in your methods section,"  co-author Jeffrey S. Mogil Department of Psychology, McGill University Alan Edwards Centre for Research on Pain, McGill University, in Montreal, told the International Science Times in an email interview. Inducing pain in the laboratory rodents is part of the job of pain research, Dr. Mogil said. "We are a pain research lab," he said. "You can't study pain without causing pain.  It is done according to accepted ethical standards, and we do nothing different from every other lab studying pain in the world.  As for 'qualms,' we would have qualms about not trying to help the hundreds of millions of people in the world who live with chronic pain day after day, sometimes for decades."

Researchers have been investigating the phenomenon of pain suppression in mice exposed to stressful or painful stimuli for the last 35 years. So-called "stress-induced analgesia" suppresses pain in the mouse and is influenced by age, gender, and prior experience to stressful or painful stimuli. Stress-induced analgesia is mediated by the same neurotransmitters that respond to opiates.

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