Document Detail

Calcium and sodium dependence of the biphasic response of the guinea-pig ileum to agonists.
MedLine Citation:
PMID:  4054215     Owner:  NLM     Status:  MEDLINE    
The isometric responses of the longitudinal smooth muscle of the guinea-pig ileum to acetylcholine and to histamine consist of a phasic contraction followed by a fade and a tonic contraction. At high agonist concentrations the fade is more pronounced and a period of lower tonus is observed in the early stage of the tonic component of the response. Experiments done in Ca2+-free medium indicate that the events responsible for the shape of the response take place in the absence of Ca2+ and of contraction. The phasic contraction was inhibited by hyperpolarization in low-Na+ medium. Small decreases in the external Na+ concentration caused a diminution of the fade. Reduction of the Na+ concentration during the early stages of the tonic response caused contraction whereas relaxation was observed at the late stages. It is proposed that the fade is dependent on a Na+-sensitive mechanism that is predominant at early but not at late stages of the responses to agonists.
V L Nouailhetas; S I Shimuta; A C Paiva; T B Paiva
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Publication Detail:
Type:  In Vitro; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  European journal of pharmacology     Volume:  116     ISSN:  0014-2999     ISO Abbreviation:  Eur. J. Pharmacol.     Publication Date:  1985 Oct 
Date Detail:
Created Date:  1985-12-18     Completed Date:  1985-12-18     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  1254354     Medline TA:  Eur J Pharmacol     Country:  NETHERLANDS    
Other Details:
Languages:  eng     Pagination:  41-7     Citation Subset:  IM    
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MeSH Terms
Acetylcholine / pharmacology
Calcium / physiology*
Guinea Pigs
Histamine / pharmacology
Ileum / drug effects
Isometric Contraction / drug effects
Membrane Potentials / drug effects
Muscle Contraction / drug effects
Muscle, Smooth / drug effects*
Potassium / pharmacology
Sodium / physiology*
Time Factors
Reg. No./Substance:
51-45-6/Histamine; 51-84-3/Acetylcholine; 7440-09-7/Potassium; 7440-23-5/Sodium; 7440-70-2/Calcium

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

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