Investigation of spinal nerve ligation-mediated functional activation of the rat brain using manganese-enhanced MRI.

To provide clear information on the cerebral regions according to peripheral neuropathy, the functional activation was investigated using manganese-enhanced magnetic resonance imaging (MEMRI). L5-spinal nerve ligation (SNL) was applied to the rats to induce neuropathic pain. Mechanical allodynia and thermal hyperalgesia were measured to confirm neuropathic pain induction following before and after gabapentin (GBP) treatment. The cerebral regions were investigated using a 4.7T MRI system in the sham, SNL, and GBP-treated SNL rats. Neuropathic pain was severely induced by SNL on the postoperative day 14, excepting the sham group. While MEMRI indicated many activation regions in the brain of SNL rats before GBP treatment, the activities were chronologically attenuated after GBP treatment. The brain regions relating SNL-induced neuropathic pain were as follows: the posterior association area of the parietal region, superior colliculus, inferior colliculus, primary somatosensory area, cingulate cortex, and cingulum bundle. SNL induced- neuropathic pain is transmitted to the primary somatosensory area and parietal region through the cingulum bundle and limbic system. These findings would be helpful for the understanding of neuropathic pain-associated process and be an accurate target for a relief of neuropathic pain.