The vasodilatory response of skin microcirculation to local heating is subject to desensitization.
BACKGROUND
In humans, local heating increases skin perfusion by mechanisms dependent on nitric oxide (NO). Because the vascular effects of NO may be subject to desensitization, we examined whether a first local thermal stimulus would attenuate the hyperemic response to a second one applied later.


METHODS
Twelve healthy young men were studied. Skin blood flow (SkBF) was measured on forearm skin with laser Doppler imaging. Local thermal stimuli (temperature step from 34 to 41 degrees C maintained for 30 minutes) were applied with temperature-controlled chambers. We also tested the influence of prior local heating on the vasodilation induced by sodium nitroprusside (SNP), a donor of NO.


RESULTS
On reheating the same spot after two hours, the response of SkBF (i.e., plateau SkBF at 30 minutes minus SkBF at 34 degrees C) was lower than during the first stimulation (mean+/-SD 404+/-212 perfusion units [PU] vs. 635+/-100 PU; P<0.001). There was no such difference when reheating after four hours (654+/-153 vs. 645+/-103 PU; P=NS). Two, but not four, hours after local heating, the response of SkBF to SNP was reduced.


CONCLUSIONS
The NO-dependent hyperemic response induced by local heating in human skin is subject to desensitization. At least one part of the mechanism implicated consists of a desensitization to the effects of NO itself.
Ciplak
Meral
M
Division de Physiopathologie Clinique, Centre Hospitalier Universitaire Vaudois et Universite de Lausanne, Lausanne, Switzerland.
Pasche
Antoine
A
Heim
Abigael
A
Haeberli
Christian
C
Waeber
Bernard
B
Liaudet
Lucas
L
Feihl
François
F
Engelberger
Rolf
R
D000222:Adaptation, Physiological; D006358:Hot Temperature; D006801:Humans; D006940:Hyperemia; D008297:Male; D008833:Microcirculation / Q000502:physiology*; D009569:Nitric Oxide / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D012039:Regional Blood Flow; D012867:Skin / Q000098:blood supply*; D013696:Temperature; D014664:Vasodilation / Q000502:physiology*; D055815:Young Adult
D009599:Nitroprusside; D009569:Nitric Oxide