2005 Volume 20 Issue 3 Pages 111-115
We employed the functional MRI (fMRI) to investigate the changes of brain activation after reducing of capsaicin-induced heat hyperalgesia. Eight healthy volunteers who have no history of brain vascular disease were enrolled in this study. Capsaicin-induced heat hyperalgesia was developed by topical application of 2% capsaicin cream to anterior surface of left forearm. First fMRI time series were taken an hour after the application of capsaicin and second fMRI time series were taken an hour after medication (Loxoprofen Na: 120 mg). As for the pain task, 45°C wet cotton was put on the region where the heat hyperalgesia was evoked by capsaicin cream. Results of first fMRI time series showed distinct activation in the thalamus, anterior cingulate cortex, supplementary motor area, and prefrontal cortex. An hour after medication, though heat hyperalgesia still remained, all participants reported improvement of pain discomfort (VAS 4.7 to 2.5). Second series fMRI showed activation only in the thalamus. These results suggest that deactivated areas (anterior cingulate, etc.) observed after medication might be involved mainly in the pain related discomfort.
