New method to erase pain

It is possible to relieve pain hypersensitivity with a new method that rekindles pain so that it can subsequently be erased, says a study.

This discovery could lead to novel means to alleviate chronic pain.

Inspired by previous work on memory, that showed that when memory is reactivated during recall its neurochemical encoding is temporarily unlocked, the researchers wanted to see whether a similar mechanism was at play during neurochemical encoding of pain sensitisation.

To this end, the researchers injected capsaicin in the foot of mice. Capsaicin, the pungent chemical in chilli pepper, triggers a burning sensation.

The procedure, which causes no physical damage, triggers pain hypersensitivity through a process of protein synthesis in the spinal cord.

Three hours later, the researchers administered a second dose of capsaicin and, at the same time, a drug that blocks protein synthesis.

The hypersensitivity then vanished rapidly. Within less than two hours, the pressure tolerated by the mice was back to 70 percent of normal.

"When the protein synthesis inhibitor is administered alone, the hypersensitivity remains," explained Yves De Koninck from laval University in Canada.

"The second injection of capsaicin is necessary to render the sensitivity to pain unstable and be able to interfere with its neurochemical reconsolidation," De Koninck noted.

The study appeared in the journal Nature Neuroscience.