Paper Info
Title
Metabolic brain activity suggestive of persistent pain in a rat model of neuropathic pain.
Abstract
Persistent pain is a central characteristic of neuropathic pain conditions in humans. Knowing whether rodent models of neuropathic pain produce persistent pain is therefore crucial to their translational applicability. We investigated the spared nerve injury (SNI) model of neuropathic pain and the formalin pain model in rats using positron emission tomography (PET) with the metabolic tracer [18F]fluorodeoxyglucose (FDG) to determine if there is ongoing brain activity suggestive of persistent pain. For the formalin model, under brief anesthesia we injected one hindpaw with 5% formalin and the FDG tracer into a tail vein. We then allowed the animals to awaken and observed pain behavior for 30min during the FDG uptake period. The rat was then anesthetized and placed in the scanner for static image acquisition, which took place between minutes 45 and 75 post-tracer injection. A single reference rat brain magnetic resonance image (MRI) was used to align the PET images with the Paxinos and Watson rat brain atlas. Increased glucose metabolism was observed in the somatosensory region associated with the injection site (S1 hindlimb contralateral), S1 jaw/upper lip and cingulate cortex. Decreases were observed in the prelimbic cortex and hippocampus. Second, SNI rats were scanned 3weeks post-surgery using the same scanning paradigm, and region-of-interest analyses revealed increased metabolic activity in the contralateral S1 hindlimb. Finally, a second cohort of SNI rats was scanned while anesthetized during the tracer uptake period, and the S1 hindlimb increase was not observed. Increased brain activity in the somatosensory cortex of SNI rats resembled the activity produced with the injection of formalin, suggesting that the SNI model may produce persistent pain. The lack of increased activity in S1 hindlimb with general anesthetic demonstrates that this effect can be blocked, as well as highlights the importance of investigating brain activity in awake and behaving rodents.
Year
DOI
Venue
2014
10.1016/j.neuroimage.2014.01.020
NeuroImage
Keywords
Field
DocType
MicroPET,FDG,Neuropathic pain,Spared nerve injury,Formalin model
Chronic pain,Cingulate cortex,Neuropathic pain,Hindlimb,Anesthesia,SNi,Nerve injury,Somatosensory system,Neuralgia,Medicine
Journal
Volume
ISSN
Citations 
91
1053-8119
1
PageRank 
References 
Authors
0.38
4
9
Name
Order
Citations
PageRank
Scott J. Thompson110.38
Magali Millecamps2111.22
Antonio Aliaga321.07
David A. Seminowicz4254.45
Lucie A. Low510.38
Barry J. Bedell6432.13
Laura S. Stone710.38
Petra Schweinhardt8132.34
M. Catherine Bushnell9111.22