Scientists Discover Neural Mechanism—and Possible Fix—for Chronic Pain

Study in mice reveals how brain circuitry goes haywire after peripheral nerve damage.

Beth Mole reports: Chronic, aching pain after an injury or operation may be all in your head. Researchers now think they’ve figured out exactly how brain wiring goes haywire to cause persistent pain—and how to fix it.

In mice with peripheral nerve damage and chronic pain from a leg surgery, a broken circuit in a pain-processing region of mammalian brains caused hyperactive pain signals that persisted for more than a month. Specifically, the peripheral nerve damage seemed to deactivate a type of interconnected brain cells, called somatostatin (SOM) interneurons, which normally dampen pain signals. Without the restraints, neurons that fire off pain signals—cortical pyramidal neurons—went wild, researchers report in Nature Neuroscience.

But the circuitry could be repaired, the researchers found. Just by manually activating those pain-stifling SOM interneurons, the researchers could shut down the rodents’ chronic pain and keep the system working properly—preventing centralized, chronic pain from ever developing.

“Our findings suggest that manipulating interneuron activity after peripheral nerve injury could be an important avenue for the prevention of pyramidal neuron over-excitation and the transition from acute postoperative pain to chronic centralized pain,” the authors, led by neuroscientist Guang Yang at New York University School of Medicine, conclude. Yang and his colleagues envision future drugs or therapies, such as transcranial magnetic stimulation, to tweak the activity of the interneurons to prevent malfunctioning pain signaling.

The study is just in mice, so it needs repeating and verifying before the line of research can move forward. That said, the work is backed by and in-line with a series of human and animal studies on chronic pain.

Earlier research found that chronic pain is coupled with alterations and hyperactivity in a pain-processing region of mammalian brains called the primary somatosensory cortex, or S1. This region is a strip across the top of the brain that spans the left and right hemisphere—like a headband over the brain. Within S1, chronic pain is linked to structural and functional changes in those pain-signaling neurons—the cortical pyramidal neurons. These changes include rearranged ion channels and higher levels of excitation … (read more)

Source: Ars Technica