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Study Shows Being Hungry Shuts off the Perception of Chronic Pain

April 9, 2018

Neuroscientists at the University of Pennsylvania found that the brain has a way to suppress chronic pain when an animal is hungry—this allows the animal to look for food while leaving intact the response to acute pain. There was a small amount of 300 brain cells found to be responsible for the ability to prioritize hunger over chronic pain. This may offer new targets for novel pain therapies.

“My lab studies hunger, and we can find neurons that make you hungry and manipulate those neurons and monitor their activity. But in the real world, things aren’t that simple.” Says J. Nicholas Betley, assistant professor of biology in Penn’s School of Arts and Sciences. “This research was to try to understand how an animal integrates multiple needs to come to a behavioral conclusion that is optimal.”

As Betley’s lab, the main focus is on hunger, particularly how hunger can alter perception. Researchers observed the way in which mice that hadn’t eaten in 24 hours responded to either acute pain or longer-term inflammatory pain, which is what has been thought to involve the sensitization of neural circuits in the brain.

Researchers found that hungry mice responded to sources of acute pain, although they seemed less responsive to inflammatory pain than mice that had been well-fed. They were observed to have similar behavior to mice that had been given an anti-inflammatory painkiller.

To find out which part of the brain was processing the intersection between hunger and pain, they experimentally turned to a group of neurons that are known to be activated by hunger (agouti-related protein, AgRP, neurons) and found that the chronic pain responses had subsided while acute pain responses remained. Betley and his colleagues found a stimulation of only a few hundred AgRP neurons that project to the parabrachial nucleus significantly suppressed inflammatory pain.

The researchers, excited by the potential clinical relevance of their findings, say if this result holds up in humans, the neural circuit offers a target for ameliorating chronic pain that is usually only addressed by opioid medications.