Heat Acclimatization in Hot Summer for Ten Weeks Suppress the Sensitivity of Sweating in Response to Iontophoretically-administered Acetylcholine

Effect of the Heat-exposure on Peripheral Sudomotor Activity Including the Density of Active Sweat Glands and Single Sweat Gland Output

“…The goal of this study was to quantify the reaction of muscarinic receptors directly stimulated for five minutes after QSART (2 mA for 5 min) with 10% ACh; a method reported previously [5,6,8]. A quantitative evaluation of the nicotine receptors was carried out.…”

“…It is painless and there is no risk associated with the subcutaneous injection; it is a simple and convenient ion permeation method that can be used for evaluation. The results of QSART to acclimatized individuals over the long term have shown a reduction in the sweating response to stimuli [5,8,15,16] of injection of ACh in native residents that move from warm areas to tropical areas and lived there for 2∼12 years showed suppression of sweating sensitivity that depended on the extension of the period of acclimatization [6]. The sweating sensitivity increased based on the extension of the deacclimatization period [7].…”

“…The temperature was measured orally and on the skin near to the capsule, using a thermistor register (K-720, Technol Seven, Yokohama, Japan). Data was recorded automatically every five seconds on the rate of sweating and the oral temperature and the temperature of the subcutaneous skin [5,8,15,16,20]. The active sweat gland density of each subject was measured by the iodine-impregnated paper method during the last stage of the QSART recording; this is a method of calculation of the average sweat gland density (count/cm 2 ) determined by scrubbing iodine-starch paper, on the subcutaneous skin, within 10∼15 seconds of the stimulation of the forearm [5].…”

“…As shown in Fig. 1B, the peripheral motor neurons involved in perspiration mediate the activity of the muscarinic receptors and axon reflex activation caused by the nicotine receptors of the peripheral C fibers in the sympathetic nerves [4][5][6][7][8]. Consequently, direct and indirect reactions can be evaluated quantitatively (Fig.…”

“…The sweating sensitivity increased based on the extension of the deacclimatization period [7]. The sweating sensitivity is the difference between the dynamic forces of the sweat glands and the sweat volume output from a single gland which is associated with induced threshold changes of the body depending on the climate conditions of the place of residence and the constant period of time living there [5,8]. Therefore, the dynamic forces of gland activity and the inhibition and suppression of single sweat gland output volume, depending on ACh sensitivity, influences the sweat volume of the whole body.…”