Document Detail

Spinal opioid receptor-sensitive muscle afferents contribute to the fatigue-induced increase in intracortical inhibition in healthy humans.
MedLine Citation:
PMID:  21317218     Owner:  NLM     Status:  MEDLINE    
We investigated the influence of spinal opioid receptor-sensitive muscle afferents on cortical changes following fatiguing unilateral knee-extensor exercise. On separate days, seven subjects performed an identical five sets of intermittent isometric right-quadriceps contractions, each consisting of eight submaximal contractions [63 ± 7% maximal voluntary contraction (MVC)] and one MVC. The exercise was performed following either lumbar interspinous saline injection or lumbar intrathecal fentanyl injection blocking the central projection of spinal opioid receptor-sensitive lower limb muscle afferents. To quantify exercise-induced peripheral fatigue, quadriceps twitch force (Q(tw,pot)) was assessed via supramaximal magnetic femoral nerve stimulation before and after exercise. Motor evoked potentials and cortical silent periods (CSPs) were evaluated via transcranial magnetic stimulation of the motor cortex during a 3% MVC pre-activation period immediately following exercise. End-exercise quadriceps fatigue was significant and similar in both conditions (Q(tw,pot) -35 and -39% for placebo and fentanyl, respectively; P = 0.38). Immediately following exercise on both days, motor evoked potentials were similar to those obtained prior to exercise. Compared with pre-exercise baseline, CSP in the placebo trial was 21 ± 5% longer postexercise (P < 0.01). In contrast, CSP following the fentanyl trial was not significantly prolonged compared with the pre-exercise baseline (6 ± 4%). Our findings suggest that the central effects of spinal opioid receptor-sensitive muscle afferents might facilitate the fatigue-induced increase in CSP. Furthermore, since the CSP is thought to reflect inhibitory intracortical interneuron activity, which may contribute to central fatigue, our findings imply that spinal opioid receptor-sensitive muscle afferents might influence central fatigue by facilitating intracortical inhibition.
Lea Hilty; Kai Lutz; Konrad Maurer; Tobias Rodenkirch; Christina M Spengler; Urs Boutellier; Lutz Jäncke; Markus Amann
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2011-02-11
Journal Detail:
Title:  Experimental physiology     Volume:  96     ISSN:  1469-445X     ISO Abbreviation:  Exp. Physiol.     Publication Date:  2011 May 
Date Detail:
Created Date:  2011-04-22     Completed Date:  2011-08-29     Revised Date:  2014-09-08    
Medline Journal Info:
Nlm Unique ID:  9002940     Medline TA:  Exp Physiol     Country:  England    
Other Details:
Languages:  eng     Pagination:  505-17     Citation Subset:  IM    
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MeSH Terms
Analgesics, Opioid / administration & dosage
Carbon Dioxide / metabolism
Electromyography / methods
Evoked Potentials, Motor / drug effects,  physiology
Exercise / physiology*
Femoral Nerve / drug effects,  metabolism,  physiology
Fentanyl / administration & dosage
Isometric Contraction / physiology
Motor Activity / drug effects,  physiology
Motor Cortex / drug effects,  physiology*
Muscle Fatigue / physiology*
Neurons, Afferent / drug effects,  metabolism,  physiology*
Quadriceps Muscle / innervation*,  metabolism
Receptors, Opioid / metabolism*
Synaptic Transmission
Transcranial Magnetic Stimulation / methods
Young Adult
Grant Support
K99 HL103786/HL/NHLBI NIH HHS; K99 HL103786-01/HL/NHLBI NIH HHS; K99 HL103786-02/HL/NHLBI NIH HHS
Reg. No./Substance:
0/Analgesics, Opioid; 0/Receptors, Opioid; 142M471B3J/Carbon Dioxide; UF599785JZ/Fentanyl

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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