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Dual effect of deafferentation on contractile characteristics and sarcoplasmic reticulum properties in rat soleus fibers

Laboratoire de Plasticité Neuromusculaire, Université des Sciences et Technologies de Lille, Villeneuve d'Ascq, France

Submitted 19 July 2004 ; accepted in final form 17 March 2005

The neural message is known to play a key role in muscle development and function. We analyzed the specific role of the afferent message on the functional regulation of two subcellular muscle components involved in the contractile mechanism: the contractile proteins and the sarcoplasmic reticulum (SR). Rats were submitted to bilateral deafferentation (DEAF group) by section of the dorsal roots L₃ to L₅ after laminectomy. Experiments were carried out in single skinned fibers of the soleus muscle. The maximal force developed by the contractile proteins was increased in the DEAF group compared with control, despite a decrease in muscle mass by 17%. The tension-pCa relationship was shifted toward lower calcium (Ca²⁺) concentrations. Different functional properties of the SR of DEAF soleus were examined by using caffeine-induced contractions. The caffeine sensitivity of the Ca²⁺ release was decreased after deafferentation and ryanodine receptor 1 isoform was expressed at a lower level. The rate of Ca²⁺ uptake was only slightly increased. The results underlined the dual effect of the afferent input on the functional regulation of both contractile proteins and SR.

neural message; muscular atrophy; contractile proteins; calcium activation properties; caffeine tensions