Fatigue-related group III/IV muscle afferent feedback facilitates intracortical inhibition during locomotor exercise
Autor: | Jacob E. Jessop, Russell S. Richardson, Dorothea S. Rosenberger, Simranjit K. Sidhu, Taylor S. Thurston, Markus Amann, Eivind Wang, Joshua C. Weavil, Chris J. McNeil |
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Rok vydání: | 2018 |
Předmět: |
0301 basic medicine
Physiology business.industry Interstimulus interval Sensory system Intrathecal Inhibitory postsynaptic potential Fentanyl 03 medical and health sciences 030104 developmental biology 0302 clinical medicine medicine.anatomical_structure nervous system Afferent Medicine Intracortical inhibition business Neuroscience 030217 neurology & neurosurgery Motor cortex medicine.drug |
Zdroj: | The Journal of Physiology. 596:4789-4801 |
ISSN: | 0022-3751 |
DOI: | 10.1113/jp276460 |
Popis: | Key points This study investigated the influence of group III/IV muscle afferents on corticospinal excitability during cycling exercise and focused on GABAB neuron-mediated inhibition as a potential underlying mechanism. The study provides novel evidence to demonstrate that group III/IV muscle afferent feedback facilitates inhibitory intracortical neurons during whole body exercise. Firing of these interneurons probably contributes to the development of central fatigue during physical activity. Abstract We investigated the influence of group III/IV muscle afferents in determining corticospinal excitability during cycling exercise and focused on GABAB neuron-mediated inhibition as a potential underlying mechanism. Both under control conditions (CTRL) and with lumbar intrathecal fentanyl (FENT) impairing feedback from group III/IV leg muscle afferents, subjects (n = 11) cycled at a comparable vastus-lateralis EMG signal (∼0.26 mV) before (PRE; 100 W) and immediately after (POST; 90 ± 2 W) fatiguing constant-load cycling exercise (80% Wpeak; 221 ± 10 W; ∼8 min). During, PRE and POST cycling, single and paired-pulse (100 ms interstimulus interval) transcranial magnetic stimulations (TMS) were applied to elicit unconditioned and conditioned motor-evoked potentials (MEPs), respectively. To distinguish between cortical and spinal contributions to the MEPs, cervicomedullary stimulations (CMS) were used to elicit unconditioned (CMS only) and conditioned (TMS+CMS, 100 ms interval) cervicomedullary motor-evoked potentials (CMEPs). While unconditioned MEPs were unchanged from PRE to POST in CTRL, unconditioned CMEPs increased significantly, resulting in a decrease in unconditioned MEP/CMEP (P 0.2). These findings reveal that feedback from group III/IV muscle afferents innervating locomotor muscle decreases the excitability of the motor cortex during fatiguing cycling exercise. This impairment is, at least in part, determined by the facilitating effect of these sensory neurons on inhibitory GABAB intracortical interneurons. |
Databáze: | OpenAIRE |
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