Why does a paper cut hurt for a moment, but a bad knee can ache for years?

A new study suggests the answer lies deep in the brainstem — and may lead to better treatments for the millions living with chronic pain.

Published in Science Advances, the research pinpoints a biological “braking system” in the brain that normally keeps short-term pain in check. But when pain becomes chronic, this system appears to malfunction, allowing pain signals to keep firing.

Researchers studied the medullary dorsal horn, a region in the brainstem that acts like a pain relay station. Here, projection neurons send pain messages up to the brain.

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During short-term inflammatory pain, the team found that these neurons actively dial down their own activity, like easing off the accelerator. But when pain becomes chronic — typically lasting more than three months — this system appears to malfunction, causing the neurons to become even more excitable and potentially contributing to the persistence of pain.

For people living with chronic pain — whether from back injuries, arthritis, cancer or migraines — this kind of breakthrough offers hope for treatments that don’t just dull the pain but fix the circuitry causing it.

Using a combination of electrophysiology and computer modelling, the researchers homed in on a key player in this process: The A-type potassium current (IA). This electrical current normally helps regulate how excitable a neuron is by helping it return to a resting state after firing, preventing overactivity.

In acute pain, IA increases, acting as a natural dampener. But in chronic pain, the team found, this current doesn’t activate, and the neurons become hyperactive.

“This is the first time we’ve seen how the same neurons behave so differently in acute versus chronic pain,” said Professor Alexander Binshtok, an expert in neurobiology.

“The fact that this natural ‘calming’ mechanism is missing in chronic pain suggests a new target for therapy. If we can find a way to restore or mimic that braking system, we might be able to prevent pain from becoming chronic.”

The results of the study have significant potential. In Australia, one in five people aged over 45 live with chronic pain, affecting their ability to live and work.

Currently, treatments include psychological therapies to retrain how the brain experiences pain, medications, physical therapy and self-management techniques.

But this study points toward more targeted strategies — ones that could restore the body’s own pain regulation systems instead of overriding them.

This article first appeared in Cosmos. Read the original here