Document Detail


"On" and "off" responses of guinea pig ureter.
MedLine Citation:
PMID:  3917613     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The in vitro guinea pig ureter responds to 5-s trains of electrical stimuli with two contractions: the first, an "on" response, occurs within 0.1-0.3 s after the onset of the stimulus train; the second, an "off" response, occurs 0.2-1.0 s after the termination of the stimulus train. Force decreases between the two responses during a time when the stimulus is still being delivered. Longer duration and/or higher frequencies of stimuli within the train are required to elicit the off response than the on response. Neither the on nor the off response appears to be neurally mediated, since both responses are unchanged by tetrodotoxin, phentolamine, atropine, and pyrilamine. Decreasing temperature from 37 to 22 degrees C decreases the amplitude of the on response and increases the amplitude of the off response. Calcium-free solution, 2 mM ethylenediaminetetraacetic acid (EDTA), 1 mM Mn2+, and 1 microM verapamil abolish the on response at a time at which the off response continues to persist. Conversely, 0.5 mM caffeine and 0.1 mM theophylline abolish the off response, whereas they only slightly reduce the on response. These data suggest that the on response depends on extracellular free calcium, whereas the off response is more dependent on bound or stored calcium.
Authors:
K W Hong; P Biancani; R M Weiss
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Publication Detail:
Type:  In Vitro; Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The American journal of physiology     Volume:  248     ISSN:  0002-9513     ISO Abbreviation:  Am. J. Physiol.     Publication Date:  1985 Jan 
Date Detail:
Created Date:  1985-02-21     Completed Date:  1985-02-21     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0370511     Medline TA:  Am J Physiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  C165-9     Citation Subset:  IM    
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MeSH Terms
Descriptor/Qualifier:
Animals
Calcium / pharmacology
Edetic Acid / pharmacology
Electric Stimulation
Female
Guinea Pigs
Magnesium / pharmacology
Male
Muscle Contraction* / drug effects
Muscle, Smooth / physiology*
Sodium / pharmacology
Theophylline / pharmacology
Ureter / drug effects,  physiology*
Verapamil / pharmacology
Grant Support
ID/Acronym/Agency:
AG-00112/AG/NIA NIH HHS; AM-16021/AM/NIADDK NIH HHS
Chemical
Reg. No./Substance:
52-53-9/Verapamil; 58-55-9/Theophylline; 60-00-4/Edetic Acid; 7439-95-4/Magnesium; 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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