Targeting an opioid receptor calms itch
From the WashU Newsroom…
A common side effect of opioids is intense itching — a problem for some patients who need the drugs for pain relief and for others fighting addiction.
Now, studying mice, researchers at Washington University School of Medicine in St. Louis have found that a drug called nalfurafine hydrochloride can deliver itch relief by targeting particular opioid receptors on neurons in the spinal cord. The drug (brand name Remitch) is approved in Japan to alleviate itching in dialysis patients with chronic kidney disease and in patients with severe liver disease. The drug also is being tested for its anti-itch effects in the U.S., but until now scientists haven’t understood how it works.
The new study suggests that the drug may be effective against many types of chronic itching that don’t respond to conventional drugs such as antihistamines. The drug targets what’s known as kappa opioid receptors on neurons in the spinal cord. While other opioid receptors on the same neurons can ramp up itching, this study shows that activating the kappa receptor significantly dials down itching.
The findings are published April 17 in the journal Cell Reports.
“The kappa opioid receptors activate a pathway that tamps down the activity of GRPR, which our lab previously identified as the first itch gene,” said senior investigator Zhou-Feng Chen, director of the Center for the Study of Itch at Washington University School of Medicine in St. Louis. “This gene relays itch signals from the spine to the brain.”