Abstract
PURPOSE: The local sweat rate response (LSR) at any given skin site is related to sudomotor activity, driven by thermal signals for the body core and mean skin temperature. Experiments using pharmacological doses of cholinergic agonist supports a role of local skin temperature on the LSR. The purpose of this study was to examine the ability of a change in local skin temperature (across the thermoneutral zone) to modulate the LSR under normal physiological conditions and stimuli.
METHODS: We examined the sweating response to a fixed sudomotor activity, driven by intradermal electrical stimulation, at three fixed skin temperature under resting conditions in 15 healthy adults. The subjects were instrumented with 7 skin temperature probes (skin), an esophageal probe to measure body core temperature (Tcore), and a local sweat rate capsule, placed on the dorsal aspect of the forearm. The subjects rested in the seated position in an environmental chamber controlled at 21, 27, and 34 °C for 60 min in successive order. The first 45 min of each hour was use to acclimate the subject to the chamber temperature. The skin was stimulated for 30 sec at 10 frequencies (ranging from 0.2 to 64 Hz, random order) to produce a transient LSR. The LSR was quantified as the area-under the sweat rate-time curve (LSR AUC) and was plotted as a function of stimulus frequency to produce a quantitative stimulus-response curve. The response curves were normalized to their peak response and then compared by ANOVA.
RESULTS: Ten of the 15 subjects produced similar stimulus- curves at all 3 temperatures. However, five of the 15 subjects showed an marked increase in the LSR when local skin temperature increased from 29.3 to 31.3 °C. However, the change in LSR response when moving from 31.3 to 34.6 °C was unremarkable.
CONCLUSION: Under our experimental conditions we found only 33% of subjects showed any impact of local temperature on the LSR to intradermal electrical stimulation.