Document Detail


Force and membrane potential during and after fatiguing, continuous high-frequency stimulation of single Xenopus muscle fibres.
MedLine Citation:
PMID:  3788614     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
'High-frequency fatigue' has been studied in isolated, short toe muscle fibres of Xenopus with recordings of tension and membrane potential during the development of fatigue and during recovery. With 70 Hz, continuous stimulation (22.5 degrees C) tension fell to 20% of the original in 11.6 +/- 4.9 s. Tension recovery occurred in two phases: an initial, fast phase to 45-80% of the original with t1/2 of about 1 s, and a second, much slower phase. The membrane potential preceding action potentials (Em) fell gradually to about -50 mV during stimulation and returned to a level of -66 to -70 mV with a time-constant of about 10 ms when the stimulation was stopped. Action potentials towards the end of stimulation were reduced in amplitude, had a slow time-course, and showed no signs of an early negative after-potential (EAP). Increasing[K]o to 14 mM (m.p. -56 to -52 mV) caused similar changes in action potential configuration, except that an EAP seemed to be present. Those action potentials were associated with potentiated twitch response reaching 70% of original tetanic tension. It is concluded that mechanical fatigue is unlikely to be due to 'fatigue' of surface action potentials per se; a more likely mechanism would be impaired t-tubule function, associated with membrane depolarization (Em becoming more positive) and possibly compounded by ionic changes of the t-tubule fluid.
Authors:
J Lännergren; H Westerblad
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Acta physiologica Scandinavica     Volume:  128     ISSN:  0001-6772     ISO Abbreviation:  Acta Physiol. Scand.     Publication Date:  1986 Nov 
Date Detail:
Created Date:  1987-01-22     Completed Date:  1987-01-22     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0370362     Medline TA:  Acta Physiol Scand     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  359-68     Citation Subset:  IM    
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MeSH Terms
Descriptor/Qualifier:
Action Potentials
Animals
Electric Stimulation / methods
Female
Membrane Potentials*
Muscle Contraction*
Perfusion
Temperature
Xenopus laevis

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


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