Overview
- A UC San Diego–led team reports in Neuron that it mapped the brain circuit that enables placebo pain relief in mice.
- Using peptide sensors co-developed with UC Davis and Max Planck Florida Institute, the team detected bursts of native opioid signals in the ventrolateral periaqueductal gray, a brainstem hub that sends pain-damping commands down the spinal cord.
- A light-activated form of naloxone called PhNX let researchers block opioid receptors at precise times and locations, which erased both morphine and placebo pain relief in that region.
- The group adapted a placebo training protocol from human studies to mice, and the learned relief carried over to other pain types, including injury-related pain.
- The study points to expectancy-based conditioning as a possible way to build drug-free pain resilience in patients, with future work planned to test training strategies before any clinical trials.