Abstract
The purpose of this study was to determine the long-term effects of spared nerve injury (SNI) on pain-related brain networks using fMRI and a novel evoked pain paradigm. Female Sprague-Dawley rats were randomly assigned to either undergo SNI (n = 7) or sham (n = 6) surgery. SNI was accomplished by transecting the left tibial and peroneal branch of the sciatic nerve, while keeping the sural nerve intact. Sham animals underwent identical surgical procedures with the exception of nerve transection. All rats were scanned using a Bruker 7 TMRI scanner 1 week prior to (pre-surgery) and 1 and 5 month/s postsurgery. During scanning, rats were anesthetizedwith# 1.5% isoflurane. Functional scans (TR = 1500 ms, TE = 35.096 ms, in plane resolution = 400 mm) were acquired during application of acetone (6 trials, 50 mL per trial, scan duration 13 minutes) to the left hindpaw. Nocifensive and anxiety-like behaviors were measured 2 weeks prior to and at 2, 5, 9, 14, and 19 weeks following surgery. Behavioral analysis revealed that SNI rats had early and sustained hypersensitivity to mechanical and thermal stimuli compared to shams, but showed no difference in anxiety-like behaviors. Region of interest analysis revealed that areas related to processing the sensory components of pain (right primary and secondary somatosensory cortex, right ventroposterior lateral thalamus) showed both early and sustained increases in BOLD activity in SNI rats compared to shams. SNI rats also showed early BOLD decreases in the left posterior (sensory/motor) cingulate cortex,whereas a late increasewas observed in a more anterior (affective) cingulate region. Our results indicate that peripheral nerve injury inducedboth early and late functional changes in pain-related brain networks that were associated with sustained thermal and mechanical hypersensitivity. Supported by American Pain Society Future Leaders in Pain Research Grant.
Published Version
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