Central and Peripheral Control of Sweating Mechanisms: Modifications by Thermal Acclimatization and Physical Training

Prolonged residence of temperate natives in the tropics produces a suppression of sweating

“…This finding indicates an attenuated pharmacological responsiveness as a component of the presumed habituation of sweating, which was shown to be combined with a delayed central drive for sweating [6] Fig. 1) from 0 to 5 min (Three asterisks denote P<0.0004).…”

“…Improved tolerance to heat in TRJ subjects may therefore involve an attenuation of the drive arising from skin temperature (Tsk). As indicated by the studies of Raynaud et al [18] and by Saat et al [19], this may contribute to the maintenance of body and skin temperatures that are higher in acclimated than in nonacclimated subjects and, consequently, in the ability for enhanced heat dissipation by dry heat loss through radiation, convection, and conduction [6], thus, using minimum amounts of sweat. This further confirms the observation that repeated exposures to heat produced changes in physiological function that increased tolerance to heat stress [14].…”

“…Upon arrival in the climatic chamber, the subject wore light indoor clothing and sat on a chair for 60 min before the acetylcholine (ACh) iontophoresis experiment. ACh iontophoresis provided a basis for the comparison of thermally and pharmacologically induced sweating responses, the volume of sweat output being an indicator of peripheral and central sudomotor activity [6,11]. The technique of the quantitative sudomotor axon reflex test (QSART) was previously described in detail [1,8,11] and was applied to evaluate directly and indirectly mediated sweat gland activation by ACh.…”

“…Many researchers have intensively investigated transitory acclimation by short-term repeated exposures to heat or exercise, and it is wellaccepted that heat tolerance is achieved by enhanced sweating starting at a lowered temperature threshold [3,5,8,10,[13][14][15][16]. On the contrary, tropical inhabitants were reported to show heat tolerance with suppressed sweating [6,12,15]. However, the magnitude and direction of thermoregulatory adjustments to heat stress of temperate natives after prolonged residence in the tropics remain to be clarified.…”

Decreased thermal sweating of central sudomotor mechanism in African and Korean men

“…The sweating center of the brain is in the preoptic area of the anterior hypothalamus and, peripherally, sympathetic postganglionic innervation is involved. Acetylcholine (ACh) is the primary transmitter of the sympathetic postganglionic innervation (Kosaka et al, ).…”