Functional MRI brain imaging studies using the Contact Heat Evoked Potential Stimulator (CHEPS) in a human volunteer topical capsaicin pain model.
Author(s)
Type
Journal Article
Abstract
Acute application of topical capsaicin produces spontaneous burning and stinging pain similar to that seen in some neuropathic states, with local hyperalgesia. Use of capsaicin applied topically or injected intradermally has been described as a model for neuropathic pain, with patterns of activation in brain regions assessed using functional magnetic resonance imaging (fMRI) and positron emission tomography. The Contact Heat Evoked Potential Stimulator (CHEPS) is a noninvasive clinically practical method of stimulating cutaneous A-delta nociceptors. In this study, topical capsaicin (1%) was applied to the left volar forearm for 15 minutes of twelve adult healthy human volunteers. fMRI scans and a visual analog pain score were recorded during CHEPS stimulation precapsaicin and postcapsaicin application. Following capsaicin application there was a significant increase in visual analog scale (mean ± standard error of the mean; precapsaicin 26.4 ± 5.3; postcapsaicin 48.9 ± 6.0; P < 0.0001). fMRI demonstrated an overall increase in areas of activation, with a significant increase in the contralateral insular signal (mean ± standard error of the mean; precapsaicin 0.434 ± 0.03; postcapsaicin 0.561 ± 0.07; P = 0.047). The authors of this paper recently published a study in which CHEPS-evoked A-delta cerebral potential amplitudes were found to be decreased postcapsaicin application. In patients with neuropathic pain, evoked pain and fMRI brain responses are typically increased, while A-delta evoked potential amplitudes are decreased. The protocol of recording fMRI following CHEPS stimulation after topical application of capsaicin could be combined with recording of evoked potentials to provide a simple, rapid, and robust volunteer model to develop novel drugs for neuropathic pain.
Date Issued
2011-10-21
Date Acceptance
2011-10-01
Citation
Journal of Pain Research, 2011, 4, pp.365-371
ISSN
1178-7090
Publisher
Dove Medical Press
Start Page
365
End Page
371
Journal / Book Title
Journal of Pain Research
Volume
4
Copyright Statement
© 2011 Shenoy et al, publisher and licensee Dove Medical Press Ltd. This is an Open Access article
which permits unrestricted noncommercial use, provided the original work is properly cited.
which permits unrestricted noncommercial use, provided the original work is properly cited.
License URL
Subjects
capsaicin
contact heat evoked potentials
fMRI
neuropathy
pain model
Publication Status
Published