SYSTEMATIC TRACING REVEALS ABERRANT RECRUITMENT OF HYPOTHALAMIC CIRCUITRY IN NEUROPATHIC PAIN

Neuropathic pain is increasingly recognized as a disorder of maladaptive plasticity across distributed brain networks, encompassing both persistent sensory hypersensitivity and affective disturbances. However, how peripheral nerve injury systematically reshapes ascending central circuits remains poorly understood, and the subcortical regions undergoing the most prominent reorganization during chronic pain have not been clearly defined. Here, using herpes simplex virus (HSV)-based trans-synaptic tracing, we systematically examined neural network-level reorganization in a mouse model of spared nerve injury (SNI). This unbiased mapping approach revealed widespread alterations across multiple brain regions, with the most pronounced changes observed in the hypothalamus, identifying it as a major site of network adaptation following peripheral nerve injury. Focusing on hypothalamic nuclei, we further combined circuit-level analyses with cell-type- and pathway-specific viral strategies, in vivo functional manipulation and recording, and sensory and affective behavioral assays to assess how chronic pain engages hypothalamic circuits. These analyses revealed coordinated changes in circuit organization, neuronal activity, and pain-related behaviors, supporting a role for hypothalamic nuclei in integrating sensory and affective dimensions of neuropathic pain. Together, these findings demonstrate the utility of systematic HSV-based tracing for uncovering large-scale pain-related network reorganization and identify the hypothalamus as a key subcortical structure involved in neuropathic pain.