Ciliary neurotrophic factor prevents unweighting-induced functional changes in rat soleus muscle

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Abstract
The purpose of the present work was to see whether changes in rat soleus characteristics due to 3 wk of hindlimb suspension could be modified by ciliary neurotrophic factor (CNTF) treatment. Throughout the tail suspension period, the cytokine was delivered by means of an osmotic pump (flow rate 16 μg ⋅ kg−1 ⋅ h−1) implanted under the hindlimb skin. In contrast to extensor digitorum longus, CNTF treatment was able to reduce unweighting-induced atrophy in the soleus. Twitch and 146 mM potassium (K) tensions, measured in small bundles of unloaded soleus, decreased by 48 and 40%, respectively. Moreover, the time to peak tension and the time constant of relaxation of the twitch were 48 and 54% faster, respectively, in unloaded soleus than in normal muscle. On the contrary, twitch and 146 mM K contracture generated in CNTF-treated unloaded and normal soleus were not different. CNTF receptor-α mRNA expression increased in extensor digitorum longus and soleus unloaded nontreated muscles but was similar in CNTF-treated unloaded muscles. The present results demonstrate that exogenously provided CNTF could prevent functional changes occurring in soleus innervated muscle subject to unweighting.