Radiocaine: An Imaging Marker of Neuropathic Injury.

Voltage-gated sodium channels (Nas) play a crucial electrical signaling role in neurons. Na-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 Na1.7, 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 blocker, has previously been used for cardiac Na1.5 imaging using positron-emission tomography (PET). In the present study, we used Radiocaine to visualize changes in neuronal Na expression 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.