Received September 23, 2004
Revised November 1, 2004
Accepted after revision December 23, 2004
Effect of rat soleus muscle overload on neuromuscular transmission efficacy during continuous and intermittent activation
Patrice Desaulniers 1,
Pierre-André Lavoie 1,
Phillip F Gardiner 2*
1 University of Montreal
2 University of Manitoba
* To whom correspondence should be addressed. E-mail: gardine2{at}ms.umanitoba.ca.
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Abstract |
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Increased neuromuscular activity is known to provoke morphological and functional adaptations at the neuromuscular synapse. Most of these changes have been documented following endurance exercise training programs. In this study, the effect of rat soleus muscle overload produced by tenotomy + voluntary wheel-cage activity on neuromuscular transmission efficacy was investigated. The overload protocol increased MEPP and EPP amplitudes by 17% and 19% respectively (both p<0.01), and increased MEPP frequency by 86% (p<0.01). EPP amplitude rundown during continuous trains of activation was attenuated by ~10% in the overloaded group (p< 0.01). Also, during intermittent activation, the overload protocol attenuated EPP amplitude rundown, mainly by enhancing EPP amplitude recovery by ~10% during the quiescent periods (p<0.01). Although the current results show that both the degree and direction of adaptation is similar to what has been observed at rat soleus NMJs following an endurance training protocol, there are important nuances between the results, suggesting different mechanisms through which these changes may occur.
Key Words:
Adaptation, Exercise, Neuromuscular junction
