Document Detail

Motor unit properties after operant conditioning of rat H-reflex.
MedLine Citation:
PMID:  11681314     Owner:  NLM     Status:  MEDLINE    
Operant conditioning of the H-reflex produces plasticity at several sites in the spinal cord, including the motoneuron. This study assessed whether this spinal cord plasticity is accompanied by changes in motor unit contractile properties. Thirty-one adult male Sprague-Dawley rats implanted for chronic recording of triceps surae electromyographic activity and H-reflex elicitation were exposed for at least 40 days to HRup or HRdown training, in which reward occurred when the H-reflex was greater than (12 HRup rats) or less than (12 HRdown rats) a criterion value, or continued under the control mode in which the H-reflex was simply measured (7 HRcon rats). At the end of H-reflex data collection, rats were anesthetized and the contractile properties of 797 single triceps surae motor units activated by intraaxonal (or intramyelin) current injection were determined. Motor units were classified as S, FR, Fint, or FF on the basis of sag and fatigue properties. Maximum tetanic force and twitch contraction time were also measured. HRdown rats exhibited a significant increase in the fatigue index of fast-twitch motor units. This resulted in a significant decrease in the percentage of Fint motor units and a significant increase in that of FR motor units. HRup conditioning had no effect on fatigue index. Neither HRup nor HRdown conditioning affected maximum tetanic force or twitch contraction time. These data are consistent with the hypothesis that conditioning mode-specific change in motoneuron firing patterns causes activity-dependent change in muscle properties.
J S Carp; X Y Chen; H Sheikh; J R Wolpaw
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Experimental brain research     Volume:  140     ISSN:  0014-4819     ISO Abbreviation:  Exp Brain Res     Publication Date:  2001 Oct 
Date Detail:
Created Date:  2001-10-29     Completed Date:  2002-03-20     Revised Date:  2014-03-25    
Medline Journal Info:
Nlm Unique ID:  0043312     Medline TA:  Exp Brain Res     Country:  Germany    
Other Details:
Languages:  eng     Pagination:  382-6     Citation Subset:  IM    
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MeSH Terms
Action Potentials / physiology
Conditioning, Operant / physiology*
H-Reflex / physiology*
Motor Neurons / physiology*
Muscle Contraction / physiology*
Muscle Fatigue / physiology
Muscle Fibers, Fast-Twitch / physiology
Muscle, Skeletal / innervation*,  physiology
Neuronal Plasticity / physiology*
Rats, Sprague-Dawley
Reaction Time / physiology
Spinal Cord / physiology*
Grant Support
Erratum In:
Exp Brain Res 2001 Nov;141(2):267, 268

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

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