Linked Life Data

12160872

Source:http://linkedlifedata.com/resource/pubmed/id/12160872

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
1
pubmed:dateCreated
2002-8-5
pubmed:abstractText
Paired pacing has been shown to potentiate contractile function of cardiac muscle, and it has been suggested that this may enhance contractile function of diaphragmatic muscle. The primary goal of this study was to study the effect of paired pacing on potentiation of contractile function of diaphragmatic muscle compared to atrial and ventricular myocardium. Diaphragmatic muscle was isolated from mouse and rat, and atrial and ventricular myocardium from dogs. Potentiation was induced by isolated extrastimuli (equal in duration and intensity to the pacing stimulus) and by repetitive extrastimuli (i.e. paired pacing) at a paced rate of 12, 30 and 60 beats/min. Baseline studies were performed while preparations were isometrically contracting at L(max) in oxygenated Krebs-Henseleit solution at 28 degrees C. Maximal force generation in response to a premature stimulus was determined at each rate by scanning the coupling interval between paced beats. Under baseline conditions, diaphragmatic muscle contracted faster than atrial and ventricular muscle. In all tissues, maximum potentiation (increase in force above baseline) was approximately 100% of baseline force, and peak potentiation occurred at shorter coupling intervals with increasing rates of stimulation. Single and paired pacing of diaphragm potentiated the contraction during which the extrastimuli were introduced, while in cardiac muscle, extrastimuli potentiated the contraction following the extrastimulus. The maximum potentiated response occurred when the extrastimulus was introduced prior to the development of peak force in diaphragmatic muscle. In contrast, in atrial and ventricular muscle, a single or paired premature stimulus potentiated the subsequent beat when delivered late during relaxation. In cardiac muscle, maximal potentiation gradually occurred following several repetitive stimuli. Following cessation of single and paired pacing, the beat following the potentiated response immediately returned to baseline in diaphragmatic muscle, while a gradual decline was evident over several subsequent beats in cardiac muscle. Increasing the bath temperature from 28 to 37 degrees C resulted in a leftward shift in the peak potentiated force vs. coupling interval curve without a decline in the magnitude of potentiated force in diaphragmatic muscle. In diaphragm muscle, exposure to ryanodine markedly decreased baseline force and maximal potentiation. We conclude that closely timed extrastimuli applied to diaphragmatic muscle can potentiate developed force in a given contraction, while in cardiac tissue a delayed stimulus potentiates the subsequent beat. These differences in contractile responsiveness are not due to differences in loading conditions, but appear to reflect intrinsic differences in calcium handling.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:status
MEDLINE
pubmed:month
Sep
pubmed:issn
1095-6433
pubmed:author
pubmed:issnType
Print
pubmed:volume
133
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
53-62
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
2002
pubmed:articleTitle
Comparison of contractile function of diaphragm and cardiac muscle in response to paired electrical stimulation.
pubmed:affiliation
Boston VA Medical Center, 150 South Huntington Avenue, Boston, MA 02130, USA. brooksww@bu.edu
pubmed:publicationType
Journal Article, Comparative Study, In Vitro, Research Support, U.S. Gov't, Non-P.H.S.