In homeostasis, somatosensory C fibre afferents are hypothesised to mediate input to the brain about interactions with external stimuli and sympathetic efference provides the output that regulates bodily functions. We aimed to test this hypothesis and whether different types of innocuous somatosensory input have differential effects. Healthy volunteers performed a muscle fatigue (hand-grip) task to exhaustion, which produces increased muscle sympathetic nerve activity (MSNA), as measured through microneurography. Participants completed the muscle fatigue task without concurrent cutaneous sensory stimulation (control) or we applied skin warming (heat pack) as a C fibre stimulation, slow brush stroking as C and Aβ fibre stimulation, or vibration as Aβ fibre stimulation, to the participant's forearm. We also measured heart rate, the duration of the hand-grip task, and ratings of pain at the end of the task. Concurrent skin warming showed increased MSNA compared to the other conditions. Tactile stimuli (brushing, vibration) were not significantly different to the control (no intervention) condition. Warming increased the pain from the muscle contraction, whereas the tactile stimuli did not. We interpret the effect of warming on MSNA as providing relevant afferent information during muscle contraction, which needed to be counteracted via vasoconstriction to maintain homeostasis. Brushing and vibration were less homeostatically relevant stimuli for the muscle contraction and hence had no significant effect. The findings add sensory specificity to our current understanding of homeostatic regulation through somatosensory afferent and sympathetic efferent pathways.

中文翻译：

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在进行肌肉疲劳的手动抓握任务时，皮肤的温暖而不是接触会增加肌肉交感神经的活动。

在体内平衡中，假设体感C纤维传入可介导大脑与外界刺激相互作用的输入，而交感神经提供调节身体功能的输出。我们旨在检验该假设以及不同类型的无害体感输入是否具有不同的影响。健康的志愿者通过筋疲力尽执行了肌肉疲劳（抓握）任务，这通过显微神经造影术测量得出增加的肌肉交感神经活动（MSNA）。参与者无需同时进行皮肤感觉刺激（对照）即可完成肌肉疲劳任务，或者我们对参与者的前臂进行了C纤维刺激下的皮肤加温（热敷），C和Aβ纤维刺激下的缓慢刷抚或Aβ纤维刺激下的振动。 。我们还测量了心率，手动任务的持续时间，以及任务结束时的疼痛等级。与其他情况相比，同时出现皮肤变暖显示MSNA升高。触觉刺激（刷，振动）与对照（无干预）条件无显着差异。温暖会增加肌肉收缩带来的疼痛，而触觉刺激则不会。我们将变暖对MSNA的影响解释为在肌肉收缩期间提供了相关的传入信息，这需要通过血管收缩来抵消，以维持体内平衡。刷洗和振动对肌肉收缩的体内稳态相关刺激较少，因此没有明显的作用。这些发现为我们目前对体感传入和交感传出途径对稳态调节的理解增加了感觉特异性。