Vascular and psychophysical effects of topical capsaicin application to orofacial tissues.
OBJECTIVE
To characterize and contrast human sensory and vascular changes produced by topical application of the algesic chemical capsaicin to the glabrous lips and tongue.


METHODS
Applications of 1% capsaicin or vehicle cream to the glabrous lips and tongue were randomized between two two-trial sessions. The capsaicin trial followed the vehicle trial for each session. Before and 5, 15, and 30 minutes after capsaicin or vehicle cream application, six parameters were recorded from the glabrous lips or the tongue dorsum: (1) burning pain intensity, as measured on a visual analog scale; (2) burning pain area, as indicated by subjects on an orofacial drawing; (3) mechanical sensitivity, as measured by a von Frey filament; (4) visual flare; (5) blood flow and temperature, as measured by laser-Doppler imaging and thermography, respectively; and (6) areas of increased temperature (hot spots), as calculated by a digital tracer from the thermographs. Data were analyzed by ANOVAs and Pearson's correlations.


RESULTS
Compared to vehicle application, capsaicin elicited burning pain, increases in blood flow and temperature, but no change in mechanical sensitivity in the glabrous lips or tongue. Greater increases in blood flow and temperature paralleled more intense burning pain and larger areas of perceived pain for the lips compared to the tongue. The location of distinct areas of increased temperature within the orofacial area differed between the capsaicin-lip and capsaicin-tongue trials.


CONCLUSIONS
The several differences between these responses to noxious stimulation of the glabrous lips and tongue may have implications for examinations of orofacial somatosensory functions.
Boudreau
Shellie A
SA
University of Toronto, Canada.
Wang
Kelun
K
Svensson
Peter
P
Sessle
Barry J
BJ
Arendt-Nielsen
Lars
L
D000328:Adult; D001831:Body Temperature / Q000187:drug effects; D002211:Capsaicin / Q000494:pharmacology*; D018592:Cross-Over Studies; D005157:Facial Pain / Q000139:chemically induced; D005260:Female; D006801:Humans; D017078:Laser-Doppler Flowmetry; D008046:Lip / Q000098:blood supply / Q000187:drug effects*; D008297:Male; D010147:Pain Measurement; D012039:Regional Blood Flow / Q000187:drug effects; D018689:Sensory System Agents / Q000494:pharmacology*; D012684:Sensory Thresholds / Q000187:drug effects; D014059:Tongue / Q000098:blood supply / Q000187:drug effects*
D018689:Sensory System Agents; D002211:Capsaicin