Sweat gland activity following thermal and cholinergic training

Heat acclimation is an important counter-mechanism to minimize heat distress. Acclimation can occur through several mechanisims including warm-water immersion. lontophoresis of pilocarpine has been shown to cause an acute sweat response, but has not been studied to assess its sustaining effects. The purpose of this investigation was to compare the physiological responses of repeated exposure to local heat vs. cholinergic agents on sweat gland function. Ten healthy. males (25.5 +/- 43 yrs-, 178.8 +/- 7.5 cm; 85 +/- 10.5 kg) served as their own controls. Sweat gland training consisted of 2-weeks of treatment, including 7-days of repeated exposure to pilocarpine to the right upper extremity (RUE), followed by 7-days of localized heat acclimation training (43 degrees C moist heating packs) to the left upper extremity (LUE). Sweat rate (SR), sweat gland density (SGD), and sweat rate per gland (S/G) were detennined following pilocarpine stimulation on day 1 (T1), day 7 (T2), and day 14 (T3) on the RUE and LUE. Baseline readings of SR (6.59 +/- 0.69 g(.)m(2.)min(-1) and 6.17 +/- 0.67) and SGD (118 +/- 3 glandS/cm(2) and 113 +/- 2) for the RUE and LUE were not significantly different on day 1 (p > 0.05). Following repeated pilocarpine iontoplioresis, the RUE exhibited a 4% decrease in SGD (114 +/- 3 glands/cm(2)) and a 50% reduction in SR (3.28 +/- 0.36 g(.)m(2.)min(-1)). Following heat acclimation the LUE showed an increase in SGD of 7% (121 +/- 3 glands/cm(2)) and a 36% increase in sweat rate (SR=8.42 0.9) g(.)m(2.)min(-1)) (p < 0.05). These data indicate that sweat glands are more productive following local heat acclimation and are less responsive following repeated exposure to cholinergic-agonists.