Scientists find proof pain-sensing cells are either male or female.

Sub: Science and tech

Sec: Health

Context:

A study led by University of Arizona Health Sciences researchers, recently published in the journal Brain, demonstrated for the first time functional sexual dimorphism in nociceptors, the nerve cells responsible for perceiving pain.

Why do we perceive pain?

Nociceptor cells have bare nerve endings and they are found across our skin, bones, joints, and muscles.
The receptors detect extreme pressure, temperature, and chemical signals released by the body when it is injured, turn them into electrical signals, and relay them to the brain via the spinal cord.
The brain finally reads the message and perceives pain.
Activation of nociceptors likely produces the same perception of pain in men and women with the only difference lies in the manner of their activation.

The nociceptor response threshold:

Previous studies have reported that the nociceptor response threshold in females is lower than that in males.
This difference could be due to peripheral nociceptor sensitisation where the threshold for pain is lowered by external factors.
To understand sexual dimorphism in nociceptors sensitisation, the research team investigated how easily pain receptors in the dorsal root ganglion — a cluster of nerve cells located near the spinal cord — could be excited.
Dr. Porecca’s lab in 2022 found that prolactin, a hormone responsible for the growth of breast tissue, also selectively promoted pain responses in female rodents.
Receptors for prolactin were expressed more in female-specific pain disorders such as endometriosis.

What is the new study?

In the new study, the researchers studied how prolactin and orexin-B affect nociceptor activation thresholds in the nerve cell samples.
On adding the sensitizing substances that lower these thresholds for activation researchers found that prolactin only sensitizes female cells and not male cells, and orexin B only sensitizes male cells and not female cells.
Studies of sleep and chronic pain also established that Orexin B, a neurotransmitter that regulates wakefulness, produced sensitisation in male rodents but not female rodents.
Study concluded that nociceptors, the fundamental building blocks of pain, are different in males and females.

Benefit of research:

It will encourage medical practitioners to factor in the sex of a patient when making decisions about pain therapies.
In clinical trials of therapies with new pain treatment mechanisms, researchers will have to be more careful about the number of men and women in the trial so that they might be alerted to effects that may only occur in one sex.