Radiocaine: An Imaging Marker of Neuropathic Injury

Voltage-gated sodium channels (Na_vs) play a crucial electrical signaling role in neurons. Na_v-isoforms present in peripheral sensory neurons and dorsal root ganglia of the spinal cord are critically involved in pain perception and transmission. While these isoforms, particularly Na_v1.7, are implicated in neuropathic pain disorders, changes in the functional state and expression levels of these channels have not been extensively studied in vivo. Radiocaine, a fluorine-18 radiotracer based on the local anesthetic lidocaine, a non-selective Na_vblocker, has previously been used for cardiac Na_v1.5 imaging using positron-emission tomography (PET). In the present study, we used Radiocaine to visualize changes in neuronal Na_vexpression after neuropathic injury. In rats that underwent unilateral spinal nerve ligation, PET/MR imaging demonstrated significantly higher uptake of Radiocaine into the injured sciatic nerve, as compared to the uninjured sciatic nerve, for up to 32 days post-surgery. Radiocaine, due to its high translational potential, may serve as a novel diagnostic tool for neuropathic pain conditions using PET imaging.