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- Ackerley, Rochelle, 1980, et al.
(author)
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Cutaneous warmth, but not touch, increases muscle sympathetic nerve activity during a muscle fatigue hand-grip task
- 2020
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In: Experimental Brain Research. - : Springer Science and Business Media LLC. - 0014-4819 .- 1432-1106. ; 238, s. 1035-1042
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Journal article (peer-reviewed)abstract
- 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 A beta fibre stimulation, or vibration as A beta 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.
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| 2. |
- Krämer, Heidrun H, et al.
(author)
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Central correlation of muscle sympathetic nerve activation during baroreflex unloading - a microneurography-positron emission tomography study
- 2014
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In: European Journal of Neuroscience. - : Wiley. - 0953-816X .- 1460-9568. ; 39:4, s. 623-629
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Journal article (peer-reviewed)abstract
- The baroreceptor reflex controls spontaneous fluctuations in blood pressure. One major control variable of the baroreflex is the sympathetic vasoconstrictor activity to muscles [MSNA; burst frequency (BF) and burst incidence (BI)], which can be quantitatively assessed by microneurography. We aimed to investigate the central regions involved in baroreflex regulation of MSNA. Healthy men (mean age 25 years) participated in three experimental sessions. (i) Microneurography recordings of MSNA from the left peroneal nerve during rest and baroreflex unloading, induced by lower body negative pressure (LBNP; -40 mmHg). If MSNA could be reliably recorded throughout this procedure (n = 15), the subjects entered the positron emission tomography (PET) experiments. The two PET sessions took place in a randomised order. Cerebral glucose metabolism (18-fluorodeoxyglucose) was analysed after: (ii) baroreflex unloading (LBNP); and (iii) control condition (lying in the LBNP chamber without suction). The PET data were analysed employing SPM8. LBNP elicited a significant increase in MSNA in all successfully recorded subjects (BI: P = 0.001; F = 5.54; BF: P < 0.001; F = 36.59). As compared with the control condition, LBNP was associated with increased PET regional glucose metabolism bilaterally in the orbitofrontal cortex (OFC; BA 11, 47). Related to the rise of BF, there was increased activation of the left OFC (BA 11); related to the rise of BI there was increased activation of the brainstem corresponding to the rostral ventrolateral medulla. Our data support a role for the ventrolateral medulla and the OFC in baroreflex-mediated control of MSNA in humans. © 2013 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.
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| 3. |
- Lautenschlager, G., et al.
(author)
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The impact of baroreflex function on endogenous pain control: a microneurography study
- 2015
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In: European Journal of Neuroscience. - : Wiley. - 0953-816X. ; 42:11, s. 2996-3003
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Journal article (peer-reviewed)abstract
- The interaction between sympathetic vasoconstrictor activity to muscles [muscle sympathetic nerve activity (MSNA), burst frequency (BF) and burst incidence (BI)] and different stress and somatosensory stimuli is still unclear. Eighteen healthy men (median age 28 years) underwent microneurography recordings from the peroneal nerve. MSNA was recorded during heat pain (HP) and cold pain (CP) alone as well as combined with different stress tasks (mental arithmetic, singing, giving a speech). An additional nine healthy men (median age 26 years) underwent the stimulation protocol with an additional control task (thermal pain combined with listening to music) to evaluate possible attentional confounders. MSNA was significantly increased by CP and HP. CP-evoked responses were smaller. The diastolic blood pressure followed the time course of MSNA while heart rate remained unchanged. The mental stress tasks further increased MSNA and were sufficient to reduce pain while the control task had no effect. MSNA activity correlated negatively with pain intensity and positively with analgesia. High blood pressure values were associated with lower pain intensity. Our study indicates an impact of central sympathetic drive on pain and pain control.
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