Résumé :
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Communication n° 376. Introduction : Concerning skeletal muscle regeneration, little information exists on differences between animal strains, long-term recovery, or differences between rapidly growing and adult animals. Such data should provide clues necessary to improve the understanding of muscle repair after injury. Objectives : We have analyzed the effect of post-natal development, strain and long term recovery on the extent of muscle functional restoration after myotoxic injury in the rat. Methods : Muscle isometric contractile properties of slow-type soleus muscle in response to nerve stimulation were measured in situ in snake venom injured muscles and contralateral muscles. Results : Some important aspects of muscular function were not fully recovered 3 weeks after injury in young (2-3 month old) Sprague-Dawley and Wistar rats. The level of recovery of some contractile parameters were also higher (specific maximal tetanic force) or lower (half-relaxation time, fatigue resistance) in young Wistar versus Sprague-Dawley rats. Concerning the long term recovery, we found that several parameters of contractile properties (half-relaxation time, degree of tetanic fusion, fatigue resistance) were not fully recovered until 6 months after injury induced in young Wistar rats. Finally, the level of functional muscle recovery 3 weeks after injury induced in juvenile rats (1 month old) was not different from that in young, adult (10 month old) and old (24 month old) Wistar rats. Conclusions : Our study demonstrates that - contrary to what is commonly believed - muscle treated by myotoxic agent does not recover rapidly in young rats. Moreover, there are strains differences in the level of muscle recovery in young rats. Finally, the functional recovery of muscle after injury do not markedly change with post-natal development and aging.
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