(322) Sensory and sympathetic innervation of mouse skeletal muscle blood and lymphatic vasculature

Zhang, J.; Huang, Wai Mun; Hughen, Ronald W.; Kang, Suk Tae; Light, Alan R.

doi:10.1016/j.jpain.2015.01.240

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“…Group III/IV muscle afferents, some of which innervate lymphatics and blood vessles within the extracellular space of skeletal muscle (Zhang et al . ), have been identified as a neural link between the CNS‐mediated decrease in motoneuronal output and the degree of peripheral fatigue (Amann et al . , a ; Sidhu et al .…”

Section: Introductionmentioning

confidence: 99%

“…Group III/IV muscle afferents, some of which innervate lymphatics and blood vessles within the extracellular space of skeletal muscle (Zhang et al 2015), have been identified as a neural link between the CNS-mediated decrease in motoneuronal output and the degree of peripheral fatigue (Amann et al 2009(Amann et al , 2011aSidhu et al 2014). Specifically, these thinly myelinated group III and unmyelinated group IV afferents are, in a dose-dependent manner, sensitive to the mechanical and metabolic stimuli associated with muscle contractions (Mense, 1977;Kniffki et al 1978;Kaufman et al 1983;Mense & Stahnke, 1983;Rotto & Kaufman, 1988;Light et al 2008) and provide feedback to the brain and spinal cord (Almeida et al 2004).…”

Section: Introductionmentioning

confidence: 99%

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Group III/IV muscle afferents limit the intramuscular metabolic perturbation during whole body exercise in humans

Blain

Mangum

Sidhu

et al. 2016

The Journal of Physiology

134

170

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Key pointsr The purpose of this study was to determine the role of group III/IV muscle afferents in limiting the endurance exercise-induced metabolic perturbation assayed in muscle biopsy samples taken from locomotor muscle.r Lumbar intrathecal fentanyl was used to attenuate the central projection of μ-opioid receptor-sensitive locomotor muscle afferents during a 5 km cycling time trial.r The findings suggest that the central projection of group III/IV muscle afferent feedback constrains voluntary neural 'drive' to working locomotor muscle and limits the exercise-induced intramuscular metabolic perturbation.r Therefore, the CNS might regulate the degree of metabolic perturbation within locomotor muscle and thereby limit peripheral fatigue. It appears that the group III/IV muscle afferents are an important neural link in this regulatory mechanism, which probably serves to protect locomotor muscle from the potentially severe functional impairment as a consequence of severe intramuscular metabolic disturbance.Abstract To investigate the role of metabo-and mechanosensitive group III/IV muscle afferents in limiting the intramuscular metabolic perturbation during whole body endurance exercise, eight subjects performed 5 km cycling time trials under control conditions (CTRL) and with lumbar intrathecal fentanyl impairing lower limb muscle afferent feedback (FENT). Vastus lateralis muscle biopsies were obtained before and immediately after exercise. Motoneuronal output was estimated through vastus lateralis surface electromyography (EMG). Exercise-induced changes in intramuscular metabolites were determined using liquid and gas chromatography-mass spectrometry. Quadriceps fatigue was quantified by pre-to post-exercise changes in potentiated quadriceps twitch torque ( QT single ) evoked by electrical femoral nerve stimulation. Although motoneuronal output was 21 ± 12% higher during FENT compared to CTRL (P < 0.05), time to complete the time trial was similar (ß8.8 min). Compared to CTRL, power output during FENT was 10 ± 4% higher in the first half of the time trial, but 11 ± 5% lower in the second half (both P < 0.01). The exercise-induced increase in intramuscular inorganic phosphate, H + , adenosine diphosphate, lactate and phosphocreatine depletion was 55 ± 30, 62 ± 18, 129 ± 63, 47 ± 14 (P < 0.001) and 27 ± 14% (P < 0.01) greater in FENT than CTRL. QT single was greater following FENT than CTRL (−52 ± 2 vs −31 ± 1%, P < 0.001) and this difference was positively correlated with the difference in inorganic phosphate (r 2 = 0.79; P < 0.01) and H + (r 2 = 0.92; P < 0.01). In conclusion, during whole body exercise, group III/IV muscle afferents provide feedback to the CNS which, in turn, constrains motoneuronal output to the active skeletal muscle. This regulatory mechanism limits the exercise-induced intramuscular metabolic perturbation, preventing an abnormal homeostatic challenge and excessive peripheral fatigue.

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Section: Introductionmentioning

confidence: 99%