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Improvement of diaphragm and limb muscle isotonic contractile performance by K+ channel blockade.

van Lunteren E, Pollarine J - J Neuroeng Rehabil (2010)

Bottom Line: Most restorative applications involve muscle shortening; however, previous studies on the effects of aminopyridines have involved muscle being held at constant length.The present study tested effects of 3,4-diaminopyridine (DAP) on isotonic contractile performance of diaphragm, extensor digitorum longus (EDL) and soleus muscles from rats.Work and peak power of both diaphragm and EDL were augmented by DAP for considerable periods of time, whereas that of soleus muscle was not affected significantly.

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Affiliation: Division of Pulmonary & Critical Care Medicine, Louis Stokes Cleveland Department of Veterans Affairs Medical Center, Case Western Reserve University, Cleveland, OH 44106, USA. exv4@cwru.edu

ABSTRACT
The K+ channel blocking aminopyridines greatly improve skeletal muscle isometric contractile performance during low to intermediate stimulation frequencies, making them potentially useful as inotropic agents for functional neuromuscular stimulation applications. Most restorative applications involve muscle shortening; however, previous studies on the effects of aminopyridines have involved muscle being held at constant length. Isotonic contractions differ substantially from isometric contractions at a cellular level with regards to factors such as cross-bridge formation and energetic requirements. The present study tested effects of 3,4-diaminopyridine (DAP) on isotonic contractile performance of diaphragm, extensor digitorum longus (EDL) and soleus muscles from rats. During contractions elicited during 20 Hz stimulation, DAP improved work over a range of loads for all three muscles. In contrast, peak power was augmented for the diaphragm and EDL but not the soleus. Maintenance of increased work and peak power was tested during repetitive fatigue-inducing stimulation using a single load of 40% and a stimulation frequency of 20 Hz. Work and peak power of both diaphragm and EDL were augmented by DAP for considerable periods of time, whereas that of soleus muscle was not affected significantly. These results demonstrate that DAP greatly improves both work and peak power of the diaphragm and EDL muscle during isotonic contractions, which combined with previous data on isometric contractions indicates that this agent is suitable for enhancing muscle performance during a range of contractile modalities.

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Effects of 3,4-diaminopyridine (DAP) on changes in isotonic peak power of diaphragm, extensor digitorum longus (EDL) and soleus during repetitive 20 Hz stimulation at a load of 40%. P values indicate results of 2-way RMANOVA testing for each panel, and asterisks (*) indicate significant differences at each load per the Newman-Kuels test.
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Figure 6: Effects of 3,4-diaminopyridine (DAP) on changes in isotonic peak power of diaphragm, extensor digitorum longus (EDL) and soleus during repetitive 20 Hz stimulation at a load of 40%. P values indicate results of 2-way RMANOVA testing for each panel, and asterisks (*) indicate significant differences at each load per the Newman-Kuels test.

Mentions: Peak power of the diaphragm was also augmented by DAP during fatigue-inducing stimulation (P = 0.02) (Figure 6). This was also the case for the EDL (P = 0.01), although the magnitude and duration of the increases were generally smaller than for the diaphragm. However, the fatigue index for peak power was not altered by DAP for either diaphragm or EDL (Figure 5B). DAP did not affect peak power of the soleus muscle over time (P = 0.53) nor did it affect the soleus muscle power fatigue index.


Improvement of diaphragm and limb muscle isotonic contractile performance by K+ channel blockade.

van Lunteren E, Pollarine J - J Neuroeng Rehabil (2010)

Effects of 3,4-diaminopyridine (DAP) on changes in isotonic peak power of diaphragm, extensor digitorum longus (EDL) and soleus during repetitive 20 Hz stimulation at a load of 40%. P values indicate results of 2-way RMANOVA testing for each panel, and asterisks (*) indicate significant differences at each load per the Newman-Kuels test.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2821379&req=5

Figure 6: Effects of 3,4-diaminopyridine (DAP) on changes in isotonic peak power of diaphragm, extensor digitorum longus (EDL) and soleus during repetitive 20 Hz stimulation at a load of 40%. P values indicate results of 2-way RMANOVA testing for each panel, and asterisks (*) indicate significant differences at each load per the Newman-Kuels test.
Mentions: Peak power of the diaphragm was also augmented by DAP during fatigue-inducing stimulation (P = 0.02) (Figure 6). This was also the case for the EDL (P = 0.01), although the magnitude and duration of the increases were generally smaller than for the diaphragm. However, the fatigue index for peak power was not altered by DAP for either diaphragm or EDL (Figure 5B). DAP did not affect peak power of the soleus muscle over time (P = 0.53) nor did it affect the soleus muscle power fatigue index.

Bottom Line: Most restorative applications involve muscle shortening; however, previous studies on the effects of aminopyridines have involved muscle being held at constant length.The present study tested effects of 3,4-diaminopyridine (DAP) on isotonic contractile performance of diaphragm, extensor digitorum longus (EDL) and soleus muscles from rats.Work and peak power of both diaphragm and EDL were augmented by DAP for considerable periods of time, whereas that of soleus muscle was not affected significantly.

View Article: PubMed Central - HTML - PubMed

Affiliation: Division of Pulmonary & Critical Care Medicine, Louis Stokes Cleveland Department of Veterans Affairs Medical Center, Case Western Reserve University, Cleveland, OH 44106, USA. exv4@cwru.edu

ABSTRACT
The K+ channel blocking aminopyridines greatly improve skeletal muscle isometric contractile performance during low to intermediate stimulation frequencies, making them potentially useful as inotropic agents for functional neuromuscular stimulation applications. Most restorative applications involve muscle shortening; however, previous studies on the effects of aminopyridines have involved muscle being held at constant length. Isotonic contractions differ substantially from isometric contractions at a cellular level with regards to factors such as cross-bridge formation and energetic requirements. The present study tested effects of 3,4-diaminopyridine (DAP) on isotonic contractile performance of diaphragm, extensor digitorum longus (EDL) and soleus muscles from rats. During contractions elicited during 20 Hz stimulation, DAP improved work over a range of loads for all three muscles. In contrast, peak power was augmented for the diaphragm and EDL but not the soleus. Maintenance of increased work and peak power was tested during repetitive fatigue-inducing stimulation using a single load of 40% and a stimulation frequency of 20 Hz. Work and peak power of both diaphragm and EDL were augmented by DAP for considerable periods of time, whereas that of soleus muscle was not affected significantly. These results demonstrate that DAP greatly improves both work and peak power of the diaphragm and EDL muscle during isotonic contractions, which combined with previous data on isometric contractions indicates that this agent is suitable for enhancing muscle performance during a range of contractile modalities.

Show MeSH
Related in: MedlinePlus