The male scent stresses out lab rodents, study says

Best of 2014 2Women have no effect on mice, but men cause a stress level comparable to a three-minute swim. Results indicate that researchers should account for these variables.

University of Alabama at Birmingham psychology professor Robert Sorge, Ph.D., recently published findings in Nature Methods that indicate the smell of male researchers causes a stress response that suppresses pain in mice and rats, while women have no effect on the test subjects.

mice-smell sSorge worked primarily alongside researchers at McGill University and then in his lab in the Department of Psychology at UAB to conduct a study that evaluated stress levels in lab rodents. Lab mice and rats were placed in a room and observed by a man or woman. The effect on the pain levels of the animals was drastically different.

The findings show that, in the presence of a male scent, rats and mice experience a stress response comparable to what they would experience being restrained in a tube for 15 minutes or swimming for three minutes. In the presence of a female scent, the rodents’ stress levels remained steady. They were also less stressed when given a woman’s shirt and a man’s shirt together.

Men secrete different amounts of testosterone-based chemicals than women do, and these alert the lab animals that there are male animals nearby, causing a spike in their stress levels. This can cause an issue with lab results, because the increased stress makes lab animals less sensitive to pain and perhaps less likely to react naturally to procedures involving learning and performance.

The results of this study could have a big impact on research, given that rats and mice comprise more than 95 percent of all lab animals. The results indicate that researchers should account for these variables in their experiments.

“Our findings suggest that one major reason for lack of replication of animal studies is the gender of the experimenter,” said Sorge. “It’s a factor that’s not currently stated in the methods sections of published papers, but it should be considered based on what we’ve discovered.”

Another option that male researchers could implement to lessen the impact on the animals would be to sit in a room with their test subjects for half an hour or more leading up to any experiments to help ease the stress effects on the animals, which will decrease over time.

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