A previously unknown sensory organ that is able to detect painful mechanical damage, such as pricks and impacts has been identified by researchers at Karolinska Institutet in Sweden. It is made up of glia cells with multiple long protrusions, which collectively go to make up a mesh-like organ within the skin.
Pain causes suffering and results in substantial costs for society. Almost one person in every five experiences chronic pain and there is a considerable need to find new painkilling drugs.
On the other, sensitivity to pain is also required for survival and it has a protective function. It prompts reflex reactions that prevent damage to tissue, such as pulling your hand away when you feel a jab from a sharp object or when you burn yourself.
Nociception is the sensory nervous system’s response to certain harmful or potentially harmful stimuli. In nociception, intense chemical (e.g., chili powder in the eyes), mechanical (e.g., cutting, crushing), or thermal (heat and cold) stimulation of sensory nerve cells called nociceptors produces a signal that travels along a chain of nerve fibers via the spinal cord to the brain. Nociception triggers a variety of physiological and behavioral responses and usually results in a subjective experience of pain in sentient beings.
This new study describes what these new pain-sensitive organ look like, how each is organized together with pain-sensitive nerves in the skin and how activation of the organ results in electrical impulses in the nervous system that result in reflex reactions and an experience of pain.
The cells that make up the organ are highly sensitive to mechanical stimuli, which explain how they can participate in the detection of painful pinpricks and pressure. In experiments, the researchers also blocked the organ and saw a resultant decreased ability to feel mechanical pain.
“Our study shows that sensitivity to pain does not occur only in the skin’s nerve fibers, but also in this recently-discovered pain-sensitive organ. The discovery changes our understanding of the cellular mechanisms of physical sensation and it may be of significance in the understanding of chronic pain,"
says Patrik Ernfors, professor at Karolinska Institutet’s Department of Medical Biochemistry and Biophysics and chief investigator for the study.
 Hind Abdo, et al. Specialized cutaneous Schwann cells initiate pain sensation. Science 16 Aug 2019: Vol. 365, Issue 6454, pp. 695-699 DOI: 10.1126/science.aax6452