EFFECT OF SKIN TEMPERATURE ON THE CHOLINERGIC SENSITIVITY OF THE HUMAN ECCRINE SWEAT GLAND

Abstract

Sweat rate has been reported to be decreased at cold skin temperatures and increased at hot skin temperatures following local drug-induced sweating. However, these skin temperatures were not within a physiological range. PURPOSE The effect of skin temperature on pilocarpine-induced sweat rate was investigated within a physiological range of skin temperatures. METHODS Thirteen subjects (30 ± 6 y; 172 ± 11 cm; 72.8 ± 11.0 kg) had forearm sweat rate measured at rest following pilocarpine iontophoresis at each of three skin temperatures in randomized order: Twarm (37.1 ± 0.9 °C), Troom (32.3 ± 1.4 °C), and Tcool (26.6 ± 1.3 °C). Skin temperature was raised and lowered ∼ 5 °C from Troom with a heating pad and ice pack, respectively. Pilocarpine iontophoresis was started after skin temperature stabilized to ± 0.5 °C for 5 min. Sweat was collected using macroducts for 15 min immediately following 5 min of iontophoretic stimulation. RESULTS Although sphericity was not assumed (P = 0.04), the Greenhouse-Geisser adjustment for RM ANOVA indicated a difference in sweat rate between the three conditions (P = 0.001). Bonferroni post-hoc analysis indicated higher sweat rates at Twarm (7.1 ± 2.7 g• m−2 • min−1; P = 0.001) and at Troom (6.2 ± 3.1 g• m−2 • min−1; P = 0.006) compared to Tcool (3.4 ± 1.7 g• m−2 • min−1). However, there was no difference between sweat rates at Twarm and Troom (P = 0.127). Such results indicate that cholinergic receptors on sweat glands may be less sensitive to agonists when skin temperature is cool. Conversely, because there was no difference in sweat rates at Twarm and Troom, it may be possible that cholinergic sensitivity is maximal or near maximal at Troom. CONCLUSION Within a physiological range of temperatures, peripheral sweat rate at Troom was decreased at Tcool but was unaffected at Twarm.