Women often prefer warmer rooms and feel cold more easily than men, and a new mouse study offers clues as to why, Live Science reported. The paper, published Oct. 28 in the Journal of Physiology, found that temperature sensors in the skin activate at higher temperatures in female mice, shifting their preferred temperature roughly 7 degrees Fahrenheit (4 degrees Celsius) higher than that of male mice. Testosterone appears to influence that difference. "You could say it's just a cute observation of no particular importance," co-author Peter McNaughton, a pharmacologist at King's College London, told Live Science. "[But] it's got practical ramifications" for designing buildings and spaces that accommodate people.
Proteins in the skin's nerve endings activate in response to warmth or cold. "You can look at them like little electrical generators in the nerve endings," said Dr. Michael Caterina, a neuroscientist at Johns Hopkins University who was not involved in the research. When those proteins activate, charged ions enter sensory nerve cells, which then send signals to the brain. Many female animals, including mice and birds, are already known to prefer slightly warmer temperatures than males. The researchers put 30 male and 27 female mice on two adjacent plates, one at 91.4 degrees Fahrenheit (33 degrees Celsius) and another that varied. A camera tracked how much time the mice spent on each plate. Both sexes spent more time on the 91.4-degree plate when the second plate was cooler. When the second plate was 100.4 F (38 C), female mice spent significantly more time on the warmer plate than males did. The average preferred surface temperature was about 89.6 F (32 C) for males and 96.8 F (36 C) for females. "Since the top of the cage was completely open, there was no question of the air temperature affecting the mice," McNaughton said. Internal and skin temperatures did not differ significantly between the sexes.
When the scientists genetically deleted the warmth-detector protein, male mice were less inclined to avoid the warmer plate, and their preferred temperature rose to about 95 F (35 C), closer to that of females. In females, deleting or blocking that protein did not have a significant effect. When they eliminated or blocked the coolness-detecting protein, both sexes avoided cool plates less strongly. Females also spent less time on the warmer plates; males' preference did not change. "Females are a little bit more responsive to activation of the cold receptor, and a little bit less responsive to activation of the warmer receptor," Caterina said, even though the temperature-sensing neurons themselves worked identically in both groups.
The team then gave male mice a drug that blocks the production of testosterone. Weeks later, those mice spent more time on the 38 C plate than males with normal testosterone. Female mice given testosterone lost their preference for warmer temperatures. Giving males forms of estrogen and progesterone did not change their preferences, and blocking those hormones in females had no effect. "So it really seems as though testosterone is the most important determinant," McNaughton said. The changes were only partial, however. "So there is something else going on that we weren't able to identify," he added. The researchers did not test people, though McNaughton noted that the same sensor proteins are present in humans and appear to behave in a similar way. The work is a mouse experiment, not a prescription for office thermostats, and Live Science noted that it is not medical advice.