Stanford Scientists Discover Brain Circuit That Fuels Chronic Pain

Researchers at Stanford University have identified a specific brain circuit that drives chronic pain, discovering that this system operates independently from the pathways responsible for acute pain. The findings, published in Nature, suggest a new direction for treating the approximately 60 million Americans who live with persistent pain.

The study reveals that the brain utilizes two distinct systems to process pain: one for immediate, protective responses and another that activates after an injury to maintain long-term pain. This discovery challenges previous understandings of how the brain manages pain signals over time.

Distinguishing Acute and Chronic Pain Circuits

Acute pain serves as a critical evolutionary response, warning animals of immediate danger and motivating them to seek healing. Chronic pain, however, is characterized by its persistence long after the initial threat or injury has dissipated.

The Stanford research team mapped these circuits using mouse brains, identifying neurons that project into the spinal cord from the rostral ventromedial medulla. The map showed that neurons involved in chronic pain are separate from those involved in acute pain.

According to senior author Xiaoke Chen, an associate professor of biology at Stanford Humanities and Sciences and an affiliate of the Wu Tsai Neurosciences Institute, the discovery that these two types of pain are completely separate was a surprise to the research team.

There is a dedicated circuit that only activates after injury, which gives us the opportunity to target the chronic pain component but leave protective acute pain intact.

Xiaoke Chen

Implications for Medical Treatment

The ability to isolate the chronic pain circuit offers a potential pathway for new medical treatments. In the study, researchers found that silencing the specific cells driving the chronic pain circuit eased the persistent pain without affecting the body’s ability to signal immediate danger through acute pain responses.

This distinction is significant because many current pain treatments may not differentiate between these two systems. A targeted approach could allow patients to find relief from chronic conditions while maintaining the protective biological function of acute pain.

Broader Public Health Context

Chronic pain is often the result of inflammation, injury, or other medical conditions. Beyond the physical sensation of pain, individuals suffering from chronic pain face an increased risk of mental health challenges and the misuse of opioids.

The research was supported in part by the NeuroChoice Initiative, a project within the Wu Tsai Neuro Big Ideas in Neuroscience. This initiative focuses on understanding the biological mechanisms of addiction, specifically regarding the risks faced by individuals who use prescription opioids to manage chronic pain.

By identifying the specific brain circuit that invents or fuels chronic pain, scientists hope to develop interventions that reduce the reliance on high-risk medications by addressing the biological root of the persistent pain signal.