Biaggioni I, Costa F, Kaufmann H
Department of Medicine, Vanderbilt University, Nashville TN 37232-2135, USA.
J Vestib Res. 1998 Jan-Feb;8(1):35-41.
There is substantial evidence that anatomical connections exist between vestibular and autonomic nuclei. Animal studies have shown functional interactions between the vestibular and autonomic systems. The nature of these interactions, however, is complex and has not been fully defined. Vestibular stimulation has been consistently found to reduce blood pressure in animals. Given the potential interaction between vestibular and autonomic pathways this finding could be explained by a reduction in sympathetic activity. However, rather than sympathetic inhibition, vestibular stimulation has consistently been shown to increase sympathetic outflow in cardiac and splanchnic vascular beds in most experimental models. Several clinical observations suggest that a link between vestibular and autonomic systems may also exist in humans. However, direct evidence for vestibular/autonomic interactions in humans is sparse. Motion sickness has been found to induce forearm vasodilation and reduce baroreflex gain, and head down neck flexion induces transient forearm and calf vasoconstriction. On the other hand, studies using optokinetic stimulation have found either very small, variable, or inconsistent changes in heart rate and blood pressure, despite substantial symptoms of motion sickness. Furthermore, caloric stimulation severe enough to produce nystagmus, dizziness, and nausea had no effect on sympathetic nerve activity measured directly with microneurography. No effect was observed on heart rate, blood pressure, or plasma norepinephrine. Several factors may explain the apparent discordance of these results, but more research is needed before we can define the potential importance of vestibular input to cardiovascular regulation and orthostatic tolerance in humans.
有大量证据表明前庭核与自主神经核之间存在解剖学联系。动物研究已显示前庭系统与自主神经系统之间存在功能相互作用。然而，这些相互作用的本质很复杂，尚未完全明确。一直以来，在动物实验中发现前庭刺激可降低血压。鉴于前庭与自主神经通路之间可能存在相互作用，这一发现可以用交感神经活动的减少来解释。然而，在大多数实验模型中，前庭刺激并未表现出交感神经抑制，反而一直显示会增加心脏和内脏血管床的交感神经输出。一些临床观察表明，前庭系统与自主神经系统之间的联系在人类中可能也存在。然而，关于人类前庭/自主神经相互作用的直接证据很少。已发现晕动病会导致前臂血管舒张并降低压力感受性反射增益，头向下颈部屈曲会诱发前臂和小腿短暂血管收缩。另一方面，尽管有明显的晕动病症状，但使用视动刺激的研究发现心率和血压变化非常小、变化不定或不一致。此外，强度足以产生眼球震颤、头晕和恶心的冷热刺激对通过微神经ography直接测量的交感神经活动没有影响。对心率、血压或血浆去甲肾上腺素也未观察到影响。有几个因素可以解释这些结果明显不一致的情况，但在我们能够确定前庭输入对人类心血管调节和直立耐受的潜在重要性之前，还需要更多的研究。
