The effect of muscle length on post-tetanic potentiation of C57BL/6 and skMLCK−/− mouse EDL muscles

Angelidis, Angelos; Vandenboom, Rene

doi:10.1007/s10974-022-09620-6

Cited by 3 publications

(1 citation statement)

References 65 publications

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“…If so, it is likely that this mechanism also contributed to the work potentiation displayed by wild‐type muscles; as a result, the genotype‐dependent difference in work we report accords with genotype‐dependent differences in myosin phosphorylation. Potential candidates for myosin phosphorylation‐independent forms of potentiation have been discussed recently (Angelidis et al, 2022; Overgaard et al, 2022).…”

Section: Discussionmentioning

confidence: 99%

Posttetanic potentiation improves neuromuscular efficiency of mouse muscle in vitro

Laidlaw¹,

Vandenboom²

2022

Physiological Reports

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Neuromuscular efficiency is defined as the ratio of work output to stimulation rate. The purpose of these experiments was to test the hypothesis that neuromuscular efficiency would be increased in proportion to posttetanic potentiation, that is, the stimulation‐induced increase in work output displayed by rodent fast‐twitch muscle. To this end, extensor digitorum longus muscles from wild‐type and skeletal myosin light chain kinase knockout (skMLCK −/− ) mice were surgically isolated and suspended in vitro (25°C). Concentric force development during shortening at 70% of maximal unloaded shortening velocity was tested at stimulus frequencies between 10 and 80 Hz both before and after a potentiating tetanus. A strong genotype‐dependent difference in the potentiation of concentric work output was observed; concentric work output of wild‐type muscles was increased by 51%–88% while that of skMLCK −/− muscles was increased by only 20%–34% across the frequencies tested. As a result, comparison of work – frequency plots revealed that the frequency required for peak and 50% peak unpotentiated work of wild‐type muscles was decreased from ~80 to 52 Hz and from ~48 to 21 Hz, respectively. By contrast, the frequency required for peak and 50% peak unpotentiated work of skMLCK −/− muscles was decreased from ~80 to 68 Hz and from ~51 to 41 Hz, respectively. Thus, wild‐type muscles with the ability to phosphorylate myosin displayed larger increases in neuromuscular efficiency than skMLCK −/− muscles (25–30 vs 10–15 Hz, respectively). This suggests that the presence of myosin phosphorylation may ameliorate or mitigate fatigue mechanisms associated with high‐frequency stimulation rates.

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Section: Discussionmentioning

confidence: 99%

Posttetanic potentiation improves neuromuscular efficiency of mouse muscle in vitro

Laidlaw¹,

Vandenboom²

2022

Physiological Reports

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Potentiation of force by extracellular potassium is not dependent on muscle length in mouse EDL muscle

Angelidis,

Overgaard,

Vandenboom

2024

American Journal of Physiology-Cell Physiology

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Increases in myofiber extracellular potassium with prolonged contractile activity can potentiate twitch force. Activity-dependent potentiation, another mechanism of force increase in skeletal muscle, has a strong dependence on muscle or sarcomere length. Thus, potassium-mediated twitch potentiation could also be length-dependent. However, this has not been previously investigated. To this end, we used isolated C57BL/6 mouse extensor digitorum longus (EDL) muscles and elicited twitches at 0.9 Lo, Lo and 1.1 Lo ( Lo refers to optimal length) in normal (5 mM) and high (10 mM) potassium solutions. Potentiation magnitude was similar to previous observations and was not significantly different between lengths (0.9 Lo: 12.3 ± 4.4 %, Lo: 12.2 ± 3.6 %, 1.1 Lo: 11.8 ± 4.8 %, values are mean ± SD). Exposure to dantrolene sodium, a compound that attenuates calcium release, reduced twitch force across lengths by ~70%. When dantrolene-affected muscles were subsequently exposed to high potassium, potentiation was not significantly different than in the absence of the former. In total, these findings provide novel information on potassium-mediated twitch potentiation.

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Force potentiation during eccentric contractions in rat skeletal muscle

Andersen

Kristensen

Nielsen

et al. 2023

Journal of Applied Physiology

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AIM: Post-activation potentiation refers to an acute enhancement of contractile properties following muscle activity. Previously, the effects of prior muscle activation on eccentric force at tetanic activation frequencies have only been sparsely reported. This paper aimed to study acute activity induced effects on eccentric force of slow and fast twitch muscles and characterize them in relation to post-activation potentiation. METHODS: We elicited eccentric contractions in isolated rat extensor digitorum longus and soleus muscles by actively lengthening muscles at a constant velocity. We assessed contractile properties by measuring force over shortly interspaced, identical eccentric and isometric contractions. We then analysed stretch force, isometric peak force, rate of force development and relaxation times. Finally, we compared the time courses for the development and cessation of changes in stretch force to known features of post-activation potentiation. RESULTS: In extensor digitorum longus muscles stretch force consistently increased in a contraction-to-contraction manner by up to 49% (95% CI: 35-64) while isometric peak force simultaneously showed minor declines (8%, 95% CI: 5-10%). The development and cessation of eccentric force potentiation coincided with development of twitch potentiation and increases in rate of force development. In soleus muscles we found no consistent eccentric potentiation. Characterization of the increase in eccentric force revealed that force only increased in the very beginning of an active stretch. CONCLUSION: Eccentric force at tetanic activation frequencies potentiates substantially in extensor digitorum longus muscles over consecutive contractions with a time course coinciding with post-activation potentiation. Such eccentric potentiation may be important in sport performance.

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The effect of muscle length on post-tetanic potentiation of C57BL/6 and skMLCK−/− mouse EDL muscles

Cited by 3 publications

References 65 publications

Posttetanic potentiation improves neuromuscular efficiency of mouse muscle in vitro

Posttetanic potentiation improves neuromuscular efficiency of mouse muscle in vitro

Potentiation of force by extracellular potassium is not dependent on muscle length in mouse EDL muscle

Force potentiation during eccentric contractions in rat skeletal muscle

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