Feminists and health advocates have long been saying that doctors and drug manufacturers shouldn’t just assume women’s bodies are simply smaller versions of men’s. A new study reveals just how wrong those kind of assumptions can be.
Published in Nature Neuroscience, the findings reveals that male and female brains actually process chronic pain using entirely different types of cells.
Previous studies have “demonstrated that men and women have different sensitivity to pain and that more women suffer from chronic pain than men,” noted Jeffrey Mogil co-author of the study and a professor of Pain Studies at McGill University and Director of the Alan Edwards Centre for Research on Pain in Toronto, Canada in a press release. “But the assumption has always been that the wiring of how pain is processed is the same in both sexes.”
The research team did not begin their study intending to examine if and how men and women process pain. Instead, they were hoping to prove the longstanding medical assumption that pain travels from the site of injury or inflammation through the nervous system via microglia, a type of cell found in the brain and spinal cord that serve as the first line of active immune defense in the central nervous system.
To find out whether pain passed through microglia, the scientists used various methods to interfere with those cells’ ability to function, and looked at whether that changed whether the mice felt pain or not.
While they did show that microglia did transmit pain though the nervous system, researchers were stunned to realize that this was only true for male mice. Tampering with the microglia function of female mice had no effect on their pain.
“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,” Mogil said.
For example, if pain is processed differently by women than men, medications currently prescribed for pain management might not be as effective for women as they are for men.
The investigators believe that instead of microglia, T cells are employed to transmit pain to the brain of females. Why there would be different pathways for pain between the sexes is still a mystery.
“Understanding the pathways of pain and sex differences is absolutely essential as we design the next generation of more sophisticated, targeted pain medications,” added Michael Salter in the same statement. Also a co-author of the study, Salter is a professor at The University of Toronto and Head of Neuroscience & Mental Health at The Hospital for Sick Children.
“We believe that mice have very similar nervous systems to humans,” Salter explained. “Especially for a basic evolutionary function like pain, so these findings tell us there are important questions raised for human pain drug development.”
The team believes that their findings could have far reaching impacts on the future of pain management. Even how biomedical research is conducted could be impacted by this revelation that women’s brains process pain so differently from men’s brains. It provides even more impetus to include female mice in research studies, to be sure there aren’t other differences that researchers might not expect.
“For the past 15 years scientists have thought that microglia controlled the volume knob on pain, but this conclusion was based on research using almost exclusively male mice,” concluded Mogil. “This finding is a perfect example of why this policy, and very carefully designed research, is essential if the benefits of basic science are to serve everyone.”