Objective To investigate the intervention of ciliary enurotrophic factors(CNTF)on weightlessness-induced muscle atrophy and its myofiber phenotype transition.Methods Tail-suspended (hindlimb unloading)of adult male Wistar rats were used to create the mode J of weightlessness-induced muscle atrophy.The effect of CNTF treatment on weightlessness-induced muscle atrophy and its myofiber phenotype transition was determined by analyzing the expression changes of MHCI/IIb and p130 or Myf5 with RT-PCR and Western blot.Results CNTF treatment in vivo markedly reversed weightlessness-induced muscle weight IOSS selectively in the slow-twitch muscle soleus.Moreover,during tail suspension,soleus weight loss and myofiber phenotype transition indicated that CNTF treatment could sigificantly attenuate the weight loss and slow to fast myofiber phenotrype transition in soleus compared with control(CNTF untreated and tail suspended).Furthermore,it was showed that the CNTF-induced intervention effect was associated with the protein level upregulation of muscle satellite cell-specific markers,P130 and Myf5.The satellite cell pool in CNTFtreated soleus was increased.Conclusion It iS firstly demonstrated that CNTF can attenuate weightlessness-induced muscle atrophy and its myofiber phenotype transition to be through the increase of satellite cell pool in soleus.