Chronic pain is processed differently by the sexes, as a woman's menstrual cycle seems to affect the abilities of receptors to block out pain. That's according to research.conducted by a team at the State University of New York (SUNY) Downstate Medical Center
Narcotic analgesics decrease pain by activating opioid receptors, which are located on nerves that transmit painful sensations. Since levels of mu, delta, and kappa opiate receptors are not thought to differ dramatically in men and women, it was difficult to understand why the effectiveness of some painkillers was dependent on sex.
Recent research has revealed that the same major types of opioid receptor interact differently, depending on sex. The spinal cord of female laboratory animals was found to contain almost five times more kappa-mu heterodimer - a complex of mu-opioid and kappa-opioid receptor - this level increased further when levels of both estrogen and progesterone were at their highest.
This synchronization with the ebb and flow of ovarian hormones could explain why drugs used to treat pain which primarily act on those receptors are more effective in women. The research suggests that physicians should take the stage of the menstrual cycle into account before deciding which drugs to prescribe to treat pain in women.
"This consideration could become even more critical in managing pain in postmenopausal and elderly women," said Alan Gintzler, PhD, professor of biochemistry. "Further research is needed to flesh out these possibilities."