New research into the pain processing of mice has found male and female mice process pain differently, and the discovery may also apply to other species, including humans. Scientists are now questioning what this means for the future of medical research, which until now, has had a strong bias towards experimenting on male mice. The study looked at immune cells called microglia, which are housed by the brain and spinal cord and are responsible for signalling to the neurons that they need to activate the feeling of pain in the event of an injury. Microglia not only help kick the feeling of pain into gear, they also regulate how severe that pain is, depending on the type of injury.
Previous studies led by pain expert, Jeffrey Mogil from McGill University in the US, suggested that microglia could play a more important role in the processing of pain for male mice than for female mice, so he decided to specifically target these immune cells to see if they would illicit a different response.
Male and female mice with chronic pain hypersensitivity were given drugs that were designed to interfere with their microglia in a way that made them more tolerant to pain. While the drugs caused the hypersensitive male mice to no longer feel heightened levels of pain, they appeared to have no effect on the females. This result occurred again and again, across a range of different scenarios.
“Whatever the manipulation is, in every case, blocking microglia or some part of the microglial system brings the pain sensitivity back to normal in male mice, and doesn’t do anything in female mice,” Mogil told Arielle Duhaime-Ross at The Verge.
The results, which were published in Nature Neuroscience, are pretty nuts, because they suggest that a crucial biological process is being governed in an entirely different way in males and females of a particular species of mammal. This means we have a pretty good idea of what could be controlling the feeling of pain in male mice, but we have no idea what that is in females (although Mogil and his team suspect it could be another type of immune cell: the T cell). And that’s a problem, because what do we use to develop pain medications and treatments for women? Mice. Source: Male and female mice process pain differently, study finds