Olfactory exposure to males, including men, causes stress and related analgesia in rodents

Sorge, R.E., Martin, L.J., Isbester, K.A., Sotocinal, S.G., Rosen, S., Tuttle, A.H., Wieskopf, J.S., (...), Mogil, J.S. Olfactory exposure to males, including men, causes stress and related analgesia in rodents (2014) Nature Methods, 11 (6), pp. 629-632. doi: 10.1038/nmeth.2935 Dr. Berkowitz had mentioned this paper…………………… The goal of this paper is to look at the responses of male and female mice to different stimuli which are intended to gauge the stress or withdrawal response to the presence or perceived presence of a male or female researcher or animal. The first experiment consisted of an injection of zymosan, an inflammatory agent. The researchers studied the facial grimacing of mice in the presence or absence of an experimenter (male or female, seated at a distance of ~0.5m). All of the four male observers elicited significant changes in grimaces, while all four of the women did not. They conducted the same study, but instead of using the researcher, they placed a shirt worn the previous night by the male or female experimenters ~0.5 away from the mice. They found that they were able to see the same trend of responses. Interesting enough, the rats did not show the response if both the male and female shirts were placed together. Next, they placed the mice in different bedding materials from either unfamiliar male mice, nonpredator male guinea pigs, rats, cats, and dogs, and once again saw the same decreases in facial grimacing. Castrated male mice, cats, and dogs did not produce the same effect in mice, suggesting that this response is likely in large part due to androgens. A longitudinal study was performed to examine their previous experiments and look at the baseline and peak responses of mice, and found that mice tested by male experimenters displayed lower baseline pain sensitivity. This stress induced analgesia in the mice is shown only when in the presence of a male. The stress caused by male experimenters is short lasting, however, it is something to consider when conducting animal research, particularly when interested in different stress responses. -MTL