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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.

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.

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Effects of 3,4-diaminopyridine (DAP) on isotonic work of diaphragm, extensor digitorum longus (EDL) and soleus as a function of load during 20 Hz stimulation. 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 2: Effects of 3,4-diaminopyridine (DAP) on isotonic work of diaphragm, extensor digitorum longus (EDL) and soleus as a function of load during 20 Hz stimulation. 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: An example of muscle length tracings of the diaphragm during isotonic contractions is depicted in Figure 1, demonstrating representative increases in muscle shortening by DAP at two loads. Work was increased by DAP for the diaphragm (P = 0.001), EDL (P = 0.007) and soleus (P = 0.01) muscles (Figure 2). For the diaphragm the increase was significant at loads ranging from 20 to 60%, whereas for the EDL and soleus the increases were significant at loads of 30 to 60%. The effects of DAP on peak power, however, were more variable among muscles (Figure 3), increasing significantly for the diaphragm (P = 0.017) and EDL (P = 0.001) but not for the soleus (P = 0.35). For the diaphragm peak power was increased at loads of 20 to 50%, whereas EDL power was increased significantly at loads of 30 to 60%. In contrast, peak power was not significantly increased for the soleus muscle at any load.


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 isotonic work of diaphragm, extensor digitorum longus (EDL) and soleus as a function of load during 20 Hz stimulation. 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 2: Effects of 3,4-diaminopyridine (DAP) on isotonic work of diaphragm, extensor digitorum longus (EDL) and soleus as a function of load during 20 Hz stimulation. 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: An example of muscle length tracings of the diaphragm during isotonic contractions is depicted in Figure 1, demonstrating representative increases in muscle shortening by DAP at two loads. Work was increased by DAP for the diaphragm (P = 0.001), EDL (P = 0.007) and soleus (P = 0.01) muscles (Figure 2). For the diaphragm the increase was significant at loads ranging from 20 to 60%, whereas for the EDL and soleus the increases were significant at loads of 30 to 60%. The effects of DAP on peak power, however, were more variable among muscles (Figure 3), increasing significantly for the diaphragm (P = 0.017) and EDL (P = 0.001) but not for the soleus (P = 0.35). For the diaphragm peak power was increased at loads of 20 to 50%, whereas EDL power was increased significantly at loads of 30 to 60%. In contrast, peak power was not significantly increased for the soleus muscle at any load.

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