Scientists studying the driving forces of chronic pain have found sex variations in the memory of pain sensitivity and stress in both humans and mice.
One of the driving forces of chronic pain appears to be the memory of earlier pain. New research led by researchers from McGill and the University of Toronto Mississauga, Canada found that there may be sex variations in the way that pain is remembered by mice and humans. There are sex differences in the memory of both pain sensitivity and stress.
Sex differences in pain sensitivity and stress
The research team found that in both men and male mice, earlier painful experiences were remembered clearly. The result is that they experienced stress and hypersensitivity to later pain when it returned to the location in which had been experienced previously.
Women and female mice did not seem to experience stress as a result of their earlier experiences of pain.
These results were a surprise finding for the scientists. Jeffrey Mogil, the E.P. Taylor Professor of Pain Studies in McGill’s Department of Psychology and Alan Edwards Centre for Research on Pain who is the senior author on the study, explained: “We set out to do an experiment looking at pain hypersensitivity in mice and found these surprising differences in stress levels between male and female mice,” explains Jeffrey Mogil, the E.P. Taylor Professor of Pain Studies in McGill’s Department of Psychology and Alan Edwards Centre for Research on Pain who is the senior author on the study. “So we decided to extend the experiment to humans to see whether the results would be similar. We were blown away when we saw that there seemed to be the same differences between men and women as we had seen in mice.”
He added: “We believe that the mice and the men were anticipating the cuff, or the vinegar, and, for the males, the stress of that anticipation caused greater pain sensitivity,” says Mogil. “There was some reason to expect that we would see increased sensitivity to pain on the second day, but there was no reason to expect it would be specific to males. That came as a complete surprise.”