Dodt C, Gunnarsson T, Elam M, Karlsson T, Wallin B G
Department of Clinical Neuroscience, Sahlgren Hospital, University of Göteborg, Sweden.
Acta Physiol Scand. 1995 Sep;155(1):41-51. doi: 10.1111/j.1748-1716.1995.tb09946.x.
The objective of this study was to test whether changes in central blood volume can induce reflex effects on sweating. Multi-unit skin sympathetic nerve activity (SSA) was recorded from the posterior cutaneous nerve of the forearm or radial nerve branches in 11 healthy volunteers. Skin electrical resistance and skin blood flow were recorded in the area innervated by the impaled nerve fascicle. Sudomotor nerve traffic and sweating was induced by whole body heating. Lower body negative pressure (LBNP) and tilting (30 degrees head up) was used for blood volume displacement from the chest to the lower body. Low levels of LBNP (5 and 10 mmHg) had no effect on blood pressure, heart rate or skin blood flow but induced a prompt inhibition of SSA and a reduced number of transient skin resistance changes (n = 9), both rapidly returning to control levels after cessation of LBNP. Quantitatively, the effect was similar at both levels of LBNP. Head up tilting also reduced SSA (n = 3, 19 tilt manoeuvres). A capacity for mental stress-induced SSA increase remained during LBNP. Spontaneous fluctuations in blood pressure did not affect SSA, arguing against arterial (high-pressure) baroreceptors modulating SSA. Consequently, the present results indicate that unloading of cardiopulmonary (low-pressure) volume receptors reduces sympathetic sudomotor nerve traffic and sweating in warm subjects. It is suggested that the reflex contributes to counteracting hypovolaemia.
本研究的目的是测试中心血容量的变化是否会对出汗产生反射性影响。在11名健康志愿者的前臂后皮神经或桡神经分支记录多单位皮肤交感神经活动（SSA）。在被穿刺神经束支配的区域记录皮肤电阻和皮肤血流量。通过全身加热诱导汗腺运动神经活动和出汗。使用下体负压（LBNP）和倾斜（头向上30度）将血容量从胸部转移到下体。低水平的LBNP（5和10 mmHg）对血压、心率或皮肤血流量没有影响，但会迅速抑制SSA，并减少短暂皮肤电阻变化的数量（n = 9），在LBNP停止后两者均迅速恢复到对照水平。定量分析，两种LBNP水平的效果相似。头向上倾斜也会降低SSA（n = 3，19次倾斜动作）。在LBNP期间，精神应激诱导SSA增加的能力仍然存在。血压的自发波动不影响SSA，这与动脉（高压）压力感受器调节SSA的观点相悖。因此，目前的结果表明，心肺（低压）容量感受器的负荷减轻会减少温暖环境中受试者的交感汗腺运动神经活动和出汗。有人认为这种反射有助于对抗血容量不足。
