Like clothing and bathrooms, pain might also come in his and hers versions.
A new Canadian study found that there may be gender differences in the way mice process pain.
"Research has demonstrated that men and women have different sensitivity to pain and that more women suffer from chronic pain than men, but the assumption has always been that the wiring of how pain is processed is the same in both sexes," said study author Jeffrey Mogil, PhD, professor of pain studies at McGill University in Quebec, in a press release.
According to Dr. Mogil and team, pain signals are transmitted through the nervous system by individual cells. The original theory was that this transmission occurred via immune system cells called microglia.
Dr. Mogil and team found that this theory may be true, but only in male mice. In female mice, another immune system cell called a T cell may do the transmitting instead.
When Dr. Mogil and team interfered with the function of microglia in a variety of ways, pain was effectively blocked in male mice. However, this interference had no effect in female mice.
This new information comes as a surprise, Dr. Mogil and team said.
Research in lab animals has traditionally been performed on male animals. Because the use of female animals has recently become more common, researchers are now finding more differences between the sexes.
This study comes in the wake of a National Institutes of Health (NIH) policy that requires the use of female animals and cell lines in preclinical research.
According to Dr. Mogil and team, this study is significant because drugs are typically designed to work with the notion that both males and females respond to pain in the same way.
Now researchers may need to develop his and her versions of pain medications.
"The realization that the biological basis for pain between men and women could be so fundamentally different raises important research and ethical questions if we want to reduce suffering,” Dr. Mogil said.
This study was published in the June issue of the journal Nature Neuroscience.
The Canadian Institutes of Health Research, Louise and Alan Edwards Foundation, NIH and SickKids Foundation funded this research. No conflicts of interest were disclosed.