Document Detail

Stretch-dependent sensitization of post-junctional neural effectors in colonic muscles.
MedLine Citation:
PMID:  23279087     Owner:  NLM     Status:  MEDLINE    
BACKGROUND: The colon undergoes distension-induced changes in motor activity as luminal contents or feces increase wall pressure. Input from enteric motor neurons regulates this motility. Here we examined stretch-dependent responses in circular muscle strips of murine colon.
METHODS: Length ramps (6-31μm s(-1) ) were applied in the axis of the circular muscle layer in a controlled manner until 5 mN isometric force was reached.
KEY RESULTS: Length ramps produced transient membrane potential hyperpolarizations and attenuation of action potential (AP) complexes. Responses were reproducible when ramps were applied every 30 s. Stretch-dependent hyperpolarization was blocked by TTX, suggesting AP-dependent release of inhibitory neurotransmitter(s). Atropine did not potentiate stretch-induced hyperpolarizations, but increased compliance of the circular layer. N(ω)-nitro-L-arginine (L-NNA) inhibited stretch-dependent hyperpolarization and decreased muscle compliance, suggesting release of NO mediates stretch-dependent inhibition. Control membrane potential was restored by the NO donor sodium nitorprusside. Stretch-dependent hyperpolarizations were blocked by L-methionine, an inhibitor of stretch-dependent K(+) (SDK) channels in colonic muscles. Loss of interstitial cells of Cajal, elicited by Kit neutralizing antibody, also inhibited responses to stretch. In presence of L-NNA and apamin, stretch responses became excitatory and were characterized by membrane depolarization and increased AP firing. A neurokinin-1 receptor antagonist inhibited this stretch-dependent increase in excitability.
CONCLUSIONS AND INFERENCES: Our data show that stretch-dependent responses in colonic muscles require tonic firing of enteric inhibitory neurons, but reflex activation of neurons does not appear to be necessary. NO causes activation of SDK channels, and stretch of muscles further activates these channels, explaining the inhibitory response to stretch in colonic muscle strips.
K-J Won; K M Sanders; S M Ward
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural     Date:  2013-01-02
Journal Detail:
Title:  Neurogastroenterology and motility : the official journal of the European Gastrointestinal Motility Society     Volume:  25     ISSN:  1365-2982     ISO Abbreviation:  Neurogastroenterol. Motil.     Publication Date:  2013 Feb 
Date Detail:
Created Date:  2013-01-22     Completed Date:  2013-09-10     Revised Date:  2014-02-04    
Medline Journal Info:
Nlm Unique ID:  9432572     Medline TA:  Neurogastroenterol Motil     Country:  England    
Other Details:
Languages:  eng     Pagination:  e101-13     Citation Subset:  IM    
Copyright Information:
© 2012 Blackwell Publishing Ltd.
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MeSH Terms
Colon / innervation,  physiology*
Enteric Nervous System / physiology*
Interstitial Cells of Cajal / physiology*
Membrane Potentials / physiology
Mice, Inbred BALB C
Muscle, Smooth / physiology*
Neurons / physiology
Potassium Channels / physiology
Grant Support
Reg. No./Substance:
0/Potassium Channels

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