Turning Over an Old Leaf

Mint oil and menthol, used by ancient Greeks and Chinese to treat sprains, joint pain, and inflammation, inspired scientists at the University of Edinburgh to discover a new pain treatment regimen.

Although seems like "common sense" that applying a cold compress to an achy joint helps curb pain, the biological mechanisms underlying why it worked were still unclear.

The Edinburgh scientists, led by Professor Susan Fleetwood-Walker and Dr. Rory Mitchell, set out to better understand cold-induced analgesia, and found cooling chemicals that had the same properties of mint oil. Applied directly to the affected area, these chemicals act through the "TRPM8" protein chemical receptor found in the skin and inhibit pain messages from being sent to the brain. TRPM8 responds to cool temperatures and cooling compounds; it is activated at moderately cool temperatures (with 50% activation at 18-19C/65F) and by menthol and icilin, which act as selective (but not totally specific) activators of the channel.

"Our discovery means that patients can be given low doses of a powerful pain killer, delivered through the skin, without side effects. We hope clinical trials on the compounds will begin within the year," said Professor Fleetwood-Walker.

Unlike orally-ingested systemic pain killers, these compounds are less likely to have toxic side effects. The researchers are hopeful that they will provide relief from chronic pain, especially that which does not respond to conventional pain killers.

Article References
'Mint' Pain Killer Takes Leaf out of Ancient Medical Texts, site accessed on 8/29/2006.

Analgesia Mediated by the TRPM8 Cold Receptor in Chronic Neuropathic Pain, site accessed on 8/29/06