Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, TX 75231, USA.
J Appl Physiol (1985). 2011 Nov;111(5):1329-34. doi: 10.1152/japplphysiol.00498.2011. Epub 2011 Aug 25.
We and others have shown that moderate passive whole body heating (i.e., increased internal temperature ∼0.7°C) increases muscle (MSNA) and skin sympathetic nerve activity (SSNA). It is unknown, however, if MSNA and/or SSNA continue to increase with more severe passive whole body heating or whether these responses plateau following moderate heating. The aim of this investigation was to test the hypothesis that MSNA and SSNA continue to increase from a moderate to a more severe heat stress. Thirteen subjects, dressed in a water-perfused suit, underwent at least one passive heat stress that increased internal temperature ∼1.3°C, while either MSNA (n = 8) or SSNA (n = 8) was continuously recorded. Heat stress significantly increased mean skin temperature (Δ∼5°C, P < 0.001), internal temperature (Δ∼1.3°C, P < 0.001), mean body temperature (Δ∼2.0°C, P < 0.001), heart rate (Δ∼40 beats/min, P < 0.001), and cutaneous vascular conductance [Δ∼1.1 arbitrary units (AU)/mmHg, P < 0.001]. Mean arterial blood pressure was well maintained (P = 0.52). Relative to baseline, MSNA increased midway through heat stress (Δ core temperature 0.63 ± 0.01°C) when expressed as burst frequency (26 ± 14 to 45 ± 16 bursts/min, P = 0.001), burst incidence (39 ± 13 to 48 ± 14 bursts/100 cardiac cyles, P = 0.03), or total activity (317 ± 170 to 489 ± 150 units/min, P = 0.02) and continued to increase until the end of heat stress (burst frequency: 61 ± 15 bursts/min, P = 0.01; burst incidence: 56 ± 11 bursts/100 cardiac cyles, P = 0.04; total activity: 648 ± 158 units/min, P = 0.01) relative to the mid-heating stage. Similarly, SSNA (total activity) increased midway through the heat stress (normothermia; 1,486 ± 472 to mid heat stress 6,467 ± 5,256 units/min, P = 0.03) and continued to increase until the end of heat stress (11,217 ± 6,684 units/min, P = 0.002 vs. mid-heat stress). These results indicate that both MSNA and SSNA continue to increase as internal temperature is elevated above previously reported values.
我们和其他人已经表明，适度的被动全身加热（即内部温度升高约 0.7°C）会增加肌肉（MSNA）和皮肤交感神经活动（SSNA）。然而，尚不清楚 MSNA 和/或 SSNA 是否会随着更严重的被动全身加热而继续增加，或者在中度加热后这些反应是否会达到平台期。本研究的目的是检验以下假设，即 MSNA 和 SSNA 会从中度到更严重的热应激持续增加。13 名受试者穿着水灌注服，至少经历了一次被动热应激，使内部温度升高约 1.3°C，同时连续记录 MSNA（n=8）或 SSNA（n=8）。热应激显著增加平均皮肤温度（Δ约 5°C，P < 0.001）、内部温度（Δ约 1.3°C，P < 0.001）、平均体温（Δ约 2.0°C，P < 0.001）、心率（Δ约 40 次/分钟，P < 0.001）和皮肤血管传导率[Δ约 1.1 任意单位（AU）/mmHg，P < 0.001]。平均动脉血压保持良好（P=0.52）。与基线相比，当以爆发频率（26 ± 14 至 45 ± 16 次/分钟，P = 0.001）、爆发发生率（39 ± 13 至 48 ± 14 次/100 次心跳，P = 0.03）或总活动量（317 ± 170 至 489 ± 150 单位/分钟，P = 0.02）表示时，MSNA 在热应激中期增加（爆发频率：26 ± 14 次/分钟，P = 0.001），并且一直持续到热应激结束（爆发频率：61 ± 15 次/分钟，P = 0.01；爆发发生率：56 ± 11 次/100 次心跳，P = 0.04；总活动量：648 ± 158 单位/分钟，P = 0.01）与中期加热阶段相比。同样，SSNA（总活动量）在热应激中期（正常体温；1,486 ± 472 至中期热应激 6,467 ± 5,256 单位/分钟，P = 0.03）增加，并一直持续到热应激结束（11,217 ± 6,684 单位/分钟，P = 0.002 与中期热应激相比）。这些结果表明，随着内部温度升高到先前报道的值以上，MSNA 和 SSNA 都会继续增加。
