This has serious consequences for their use in pain and other biomedical studies
Many people, including researchers themselves, are concerned about the lack of reliability and replicability of nonhuman animal (animal) models in biomedical research (for detailed summaries see also and). Often, when results cannot be replicated, the reasons remain unclear. Now, some light has been shed on why this is so. It turns out that the scent of the experimenter wreaks havoc on the data that are collected.
Male experimenter odors cause stress and analgesia in rats
A team of researchers has recently reported that human male, but not human female odors, cause stress and analgesia in laboratory mice and rats. Both male and female rodents become less sensitive to pain. A summary of the research article titled “Olfactory exposure to males, including men, causes stress and related analgesia in rodents” can be found in an essay called “The scent of a man: Gender of experimenter has big impact on rats’ stress levels, explains lack of replication of some findings.” Pain inhibition “was shown by placing cotton T shirts, worn the previous night by male or female experimenters, alongside the mice; the effects were identical to those caused by the presence of the experimenters, themselves.”