Objective To investigate the expression of MicroRNA-1/133a in denervated skeletal muscle at different periods.Methods From April 2012 to December 2012,a total of 54 Sprague-Dawle rats weighted (200 ± 10) g were used.They were randomly divided into 9 groups,each group of 6.The right sciatic nerve was cut off in rats (experimental group),with the left one being sham operation(control group)at various time points(0 h,8 h,1 d,3 d,1 weeks,2 weeks,3 weeks,4 weeks,8 weeks).Then after rats were sacrificed by spinal dislocation,the muscle sample(gastrocnemius,extensor digitorum longus and soleus)were harvested and weighed,then stored at-70 degrees.MicroRNA-1/133a were detected in each muscle specimens by RT-PCR.The ultrastructural changes of each muscle specimens at different periods were observed by electron microscopy.Results The muscle wet weight ratio of experimental group decreased gradually over time.Observed by electron microscopy,the different types of muscle fiber were disordered arrangement at different time points.RT-PCR was performed to quantitatively analyze miRNA-1/133a expressions of the fast-twitch muscles (i.e.,gastrocnemius and extensor digitorum longus)and slow-twitch muscle (soleus).In the control group,miRNA-133 and miRNA-1 expression in the soleus muscles were maintained at a certain level,whereas in the experimental group,these first decreased and then increased,with the lowest at 4 weeks and the highest at 8 weeks.For the gastrocnemius and extensor digitorum longus muscles in the experimental group,the expressions changed with time,whereas in the control group,these were maintained at a certain level.In the experimental group,miRNA-133 at 1 week was the lowest and was always low for all time points,whereas in the experimental group,miRNA-1 expression at 3 days was at a minimum level.The expression of MicroRNA-1/133a in the experimental group had significant differences than the control group (P ＜ 0.05).Conclusion MicroRNA-1/ 133a have differrent expression in rat fast and slow denervation muscle atrophy,presumably.It is a key point in the regulation of fast-twitch and slow-twitch muscle aspects.