MONDAY, April 28, 2014 (HealthDay News) — The scent of male researchers, but not females, triggers stress in lab mice and rats — stress that might alter the findings of experiments, a new study suggests.
Researchers at McGill University in Montreal, Canada, found that when men were in the lab, mice and rats had a stress response equal to being restrained for 15 minutes or being forced to swim for three minutes.
This stress made both male and female rodents less sensitive to pain and caused them to respond differently in behavioral tests, the team noted.
On the other hand, female researchers caused no stress reaction in the lab animals, according to the study published online April 28 in the journal Nature Methods.
In order to confirm that this stress response was related to scent, the researchers exposed mice to cotton T-shirts that had been worn by male and female researchers. The stress reaction was the same as that caused by the presence of researchers.
Further investigation revealed that the mice were stressed by chemicals called pheromones that men emit from their armpits at higher levels than women. Because all mammals share the same pheromones, these chemical signals alert the rodents that a male is nearby.
The findings could have real implications for rodent-based research everywhere, the Canadian team said. For one thing, they point out that scientists often find it difficult to replicate findings from animal research, which has led to concerns over the reliability of these studies.
However, “our findings suggest that one major reason for lack of replication of animal studies is the gender of the experimenter — a factor that’s not currently stated in the methods sections of published papers,” study leader Robert Sorge, a psychology professor at the University of Alabama, Birmingham, said in a McGill University news release. He led the study while a postdoctoral fellow at McGill.
The “problem is easily solved by simple changes to experimental procedures,” study senior author Jeffrey Mogil, a psychology professor at McGill, added in the news release.
“For example, since the effect of males’ presence diminishes over time, the male experimenter can stay in the room with the animals before starting testing. At the very least, published papers should state the gender of the experimenter who performed the behavioral testing,” Mogil said.
The Hastings Center discusses animal research ethics.