Women and men experience pain, particularly chronic pain, very differently. The ability of some opioids to relieve pain also differs between women and men. While it has been recognized since the mid-nineties that some narcotic analgesics are more effective in women than men, the reason for this difference was largely unknown.
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 receptorsthe three main types of opioid receptor in the brain and spinal cordare not thought to differ dramatically in men and women, it was difficult to understand why the effectiveness of some painkillers is dependent on sex.
Now, research supported by the National Institute of Drug Abuse (NIDA) 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 heterodimera complex of mu-opioid and kappa-opioid receptorthan the spinal cord of male animals. Furthermore, the amount of mu-kappa heterodimer in the spinal cord of the females was about four times higher when their levels of estrogen and progesterone were at their peak. Subsequently, researchers found that both estrogen and progesterone are critical for the formation of mu-kappa opioid receptor heterodimers.
This research was conducted by Alan Gintzler, PhD, professor of biochemistry, Department of Obstetrics and Gynecology, and his senior collaborators Sumita Chakrabarti, PhD, and Nai-Jiang Liu, PhD, at the State University of New York (SUNY) Downstate Medical Center
The discovery of a mu-kappa opioid receptor complex that is more prevalent in the spinal cord of females than males and that is synchronized with the ebb and flow of ovarian hormones could explain why drugs used to treat pain, such as pentazocine, nalbuphine, and butorphanolwhic
|Contact: Alan Gintzler, Ph.D.|
SUNY Downstate Medical Center