After pleasure, we discover that men and women also differ in pain.
For the first, it would be a difference in the concentration of nerve endings that make the clitoris much more sensitive than the penis. For the second, it would rather be a difference at the level of the mechanisms which make us sensitive to pain.
Pain receptors are activated by different pathways
A study from the University of Arizona (USA) has just shown that the pain receptors (nociceptors) of men and women are activated by different signaling pathways, which could explain why certain pains affect women more than men. Their discovery, presented on June 3, 2024 in the journal Brain, could also make it possible to more effectively treat ailments such as migraine, which mainly affects women.
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Nociceptors (from Latin wedding, which means "to harm" or "to be harmful") respond to harmful stimuli, such as burning heat or a strong blow, in order to alert the body and trigger a protective response. These pain receptors can become more or less sensitive, meaning that the threshold at which they will activate can vary.
Thus, a sensitized nociceptor can feel pain with a stimulus that would not normally be strong enough to activate it. Triggering physiological phenomena such as allodynia (when pain is triggered by a normally painless stimulus) and hyperalgesia (when a painful stimulus causes more pain than usual).
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Female nociceptors are sensitized by prolactin
It is in this process of sensitization of nociceptors that there would be a difference between men and women. The authors of the study have highlighted that prolactin (a hormone that participates in particular in lactation) sensitizes the nociceptors of women, but not those of men. However, this hormone is present in both sexes, even if its level is normally higher in women (before the menopause).
However, researchers have observed In vitro that nociceptors of female mice are activated by prolactin, whereas this hormone has no effect on nociceptors of male mice. This sensitization led to hyperexcitability of these sensory neurons only in females. This difference between the sexes would be due to a higher expression of the prolactin receptor in females than in males.
Treat pain in a more targeted manner
The researchers were able to verify their observations by using pain-sensing neurons from four men and three women. As in mice, prolactin sensitized the nociceptors in humans, but only in women. Women also had a much higher expression of the prolactin receptor in neurons involved in pain sensation, which could explain their greater sensitivity to this hormone.
While male nociceptors could be sensitized by other molecules, orexins (neurotransmitters that stimulate appetite, among other things) have no effect on female nociceptors.
“ The results of this study are robust and support the remarkable conclusion that nociceptors, the fundamental "building blocks" of pain, are different in men and women., resume in a communicates Frank Porreca, director of the Center for Pain and Addiction at the University of Arizona (USA) and author of the study. This gives us an opportunity to treat pain specifically. »
Following this discovery, researchers will be able to test more targeted and therefore perhaps more effective pain treatments. For example, the dopamine is known to inhibit the production of prolactin, which could constitute an alternative to specifically treat certain pains in women by avoiding the hypersensitization of their nociceptors.
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