Document Detail

Transient hyperpolarization of non-contracting muscle fibres in anaesthetized rats.
MedLine Citation:
PMID:  1335507     Owner:  NLM     Status:  MEDLINE    
1. Following laminectomy, the L5 ventral roots of anaesthetized rats were split and approximately half of the nerve fibres were stimulated at 40 Hz. Resting membrane potentials were then measured in previously contracting and non-contracting soleus muscle fibres. 2. In the non-contracting soleus fibres there was a post-tetanic increase in mean resting potential (from -82.2 +/- 7.1 (S.D.) to -91.6 +/- 8.7 mV) which was similar to that in contracting fibres (from -83.02 +/- 6.1 to -91.3 +/- 7.3 mV). In both types of fibres the hyperpolarizing responses (HRs) were evidently due to increased sodium pump activity since they could be abolished by the addition of ouabain (1 x 10(-4) M) to the bathing fluid. 3. The beta-adrenergic antagonist, propranolol, completely suppressed HRs in the non-contracting fibres and produced moderate reductions in the contracting ones. The alpha-adrenergic blocking agent, phentolamine, had no effect on the contracting fibres and only a modest, inhibitory, one on the non-contracting fibres. 4. On the basis of the above drug actions it appeared that catecholamines were necessary for the full development of HRs in contracting and non-contracting fibres; noradrenaline, released from intramuscular sympathetic nerve endings, may have been involved. 5. The increased sodium pump activity in the non-contracting fibres would serve to moderate the rise in interstitial [K+] caused by K+ efflux from the contracting fibres. By preventing passive depolarization, due to the rise in interstitial [K+], the sodium pump would also maintain the availability of non-contracting fibres for subsequent recruitment.
S Kuiack; A McComas
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The Journal of physiology     Volume:  454     ISSN:  0022-3751     ISO Abbreviation:  J. Physiol. (Lond.)     Publication Date:  1992 Aug 
Date Detail:
Created Date:  1993-02-02     Completed Date:  1993-02-02     Revised Date:  2010-09-07    
Medline Journal Info:
Nlm Unique ID:  0266262     Medline TA:  J Physiol     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  609-18     Citation Subset:  IM    
Department of Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada.
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MeSH Terms
Electric Stimulation
Membrane Potentials
Muscle Contraction / drug effects,  physiology*
Muscles / drug effects,  innervation,  physiology
Ouabain / pharmacology
Phentolamine / pharmacology
Propranolol / pharmacology
Rats, Wistar
Sodium-Potassium-Exchanging ATPase / drug effects,  physiology*
Reg. No./Substance:
50-60-2/Phentolamine; 525-66-6/Propranolol; 630-60-4/Ouabain; EC ATPase

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

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