The assumption about how we experience pain has been largely unchanged for decades.
If you stub your toe or burn your hand, the message that you’ve experienced an unpleasant sensation — pain — is forwarded to your brain.
Your brain then decides how to react.
But a new discovery regarding the role of the peripheral nervous system — the messenger in these scenarios — could change our understanding of the pain response and even alter the course of pain management.
Turning up the volume
A study at the University of Leeds in the United Kingdom determined that the peripheral nervous system does more than just pass sensory information — pain, temperature, and an object’s solidity — along to the central nervous system.
In fact, the peripheral nervous system could be capable of interpreting data and can even react by adjusting how much feedback the central nervous system receives.
Simply put, the peripheral system may act more like a volume knob than an on/off switch for processing and passing on pain signals to the brain.
The neuroscientist researchers describe the ganglia (the thousands of nerve bundles throughout the body that comprise the peripheral nervous system) as having “mini brains” intelligent enough to interpret and modify the signals they forward to the central nervous system.
The ganglia communicate between each other via the signaling molecule GABA, a process previously believed to only take place in the central nervous system.
New ways to battle pain
The findings present new opportunities for pain and pain medication researchers to target the peripheral nervous system rather than target the central nervous system as current drugs do.
Pain relief drugs like opioids that target the central nervous system have negative side effects and the potential to cause tolerance issues, addiction, and overdose.
Drugs for targeting the peripheral nervous system may be nonaddictive and perhaps be given in higher doses to increase effectiveness.
“The major treatments — opioids, for one — administer molecules small and simple enough to cross the blood-brain barrier,” Nikita Gamper, professor of neuroscience at the University of Leeds, and the study’s author, told Healthline. “But small molecules are difficult to develop to the point where they’re specific but without side effects. There’s always a trade-off between efficacy and side effects. There are less addictive drugs for pain than opioids, like ibuprofen, but they’re less effective.”
Drugs that are designed to target the peripheral nervous system, on the other hand, can administer molecules that don’t have to cross the blood-brain barrier.
They’re basically larger molecules that could potentially separate the side effects from the pain-relieving properties. Dosing could also be higher if the drug doesn’t reach the brain.
“Opioids can remove all kinds of pain, even very strong pain, but the dosage is a problem,” Gamper says. “You could go to such a dose that the patient becomes a vegetable. But if we can separate out the psychotropic effects, there’s the possibility of relieving pain without making the patient high or sleep.”
“We need to start thinking about therapies based on this phenomenon of intelligent ganglia,” Gamper says.
Optimism among medical professionals
Members of the medical community are cautiously optimistic.
“These agents that target the peripheral nervous system may have fewer associative events like sedation or balance disturbances or adverse effects like depression, hormonal disturbances, and others — than opioids,” Dr. W. Clay Jackson, vice president of the board of the Academy of Integrative Pain Management, told Healthline. “However, it is paramount that we realize the limitations of pharmacologic therapies for pain and instead provide access to nonpharmacologic therapies like biofeedback, acupuncture, meditation, and physical therapy. All patients should have adequate access to all known therapies with known efficacy and minimal adverse effects.”
The Leeds study took place over five years and only involved rats.
The next step would be to replicate the study with humans.
Drug medications based on this research could be developed within the next 15 to 20 years.