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

The purpose of the present work was to see whether changes in rat soleus ch aracteristics due to 3 wk of hindlimb suspension could be modified by cilia ry neurotrophic factor (CNTF) treatment. Throughout the tail suspension per iod, the cytokine was delivered by means of an osmotic pump (flow rate 16 p g kg(-1) h(-1)) implanted under the hindlimb skin. In contrast to extensor digitorum longus, CNTF treatment was able to reduce unweighting-induced atr ophy in the soleus. Twitch and 146 mM potassium (K) tensions, measured in s mall bundles of unloaded soleus, decreased by 48 and 40%, respectively. Mor eover, 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 nor mal muscle. On the contrary, twitch and 146 mM K contracture generated in C NTF-treated unloaded and normal soleus were not different. CNTF receptor-al pha mRNA expression increased in extensor digitorum longus and soleus unloa ded nontreated muscles but was similar in CNTF-treated unloaded muscles. Th e present results demonstrate that exogenously provided CNTF could prevent functional changes occurring in soleus innervated muscle subject to unweigh ting.