Capsaicin-induced thermal hyperalgesia and sensitization in the human trigeminal nociceptive pathway: an fMRI study.

Full Abstract

The aim of this study was to differentiate the processing of nociceptive information, matched for pain intensity, from capsaicin-induced hyperalgesic vs. control skin at multiple levels in the trigeminal nociceptive pathway. Using an event-related fMRI approach, 12 male subjects underwent three functional scans beginning 1 h after topical application of capsaicin to a defined location on the maxillary skin, when pain from capsaicin application had completely subsided. Brush and two levels of painful heat (low-Thermal-1 and high-Thermal-2) were applied to the site of capsaicin application and to the mirror image region on the opposite side. Temperatures for each side were set to evoke perceptually matched pain (mean temperatures [capsaicin/control]:
Thermal-1=38.4/42.8 degrees C; Thermal-2=44.9/47.8 degrees C). We found differences in activation patterns following stimuli to treated and untreated sides in sensory circuits across all stimulus conditions. Across the trigeminal nociceptive pathway, Thermal-2 stimulation of hyperalgesic skin evoked greater activation in trigeminal ganglion and nucleus, thalamus, and somatosensory cortex than the control side. Thus, trigeminal nociceptive regions showed increased activation in the context of perceptually equal pain levels. Beyond these regions, contrast analyses of capsaicin vs. control skin stimulation indicated significant changes in bilateral dorsolateral prefrontal cortex and amygdala. The involvement of these emotion-related regions suggests that they may be highly sensitive to context, such as prior experience (application of capsaicin) and the specific pain mechanism (hyperalgesic vs. normal skin).

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Author information

Author/s: Moulton, Eric A (EA); Pendse, Gautam (G); Morris, Susie (S); Strassman, Andrew (A); Aiello-Lammens, Matthew (M); Becerra, Lino (L); Borsook, David (D);

Affiliation: P.A.I.N. Group, Brain Imaging Center, McLean Hospital, 115 Mill Street, Belmont, MA 02478, USA. emoulton(-atsign-)mclean.harvard.edu

Grants: NS042721 (Agency:NINDS NIH HHS) ; R01 NS042721-03 (Agency:NINDS NIH HHS)

Journal and publication information

Publication Type: Journal Article; Research Support, N.I.H., Extramural

Journal: NeuroImage (Neuroimage), published in United States. (Language: eng)

Reference: 2007-May; vol 35 (issue 4) : pp 1586-600

Dates: Created 2007/04/17; Completed 2007/06/11; Revised 2008/11/21;

PMID: 17407825, status: MEDLINE (last retrieval date: 12/26/2008)

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

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MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Administration, Topical
Adult
Capsaicin - pharmacology
Female
Hot Temperature
Humans
Hyperalgesia - chemically induced; physiopathology
Image Processing, Computer-Assisted
Individuality
Logistic Models

Associated Chemicals: Capsaicin (404-86-4)

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