Abstract: Objective To observe the effect of Xiaoyingqiangjitang on the ultrastructure of motor end-plate of skeletal muscle in rats with hyperthyroid myopathy, and changes of acetylcholin esterase (AchE).Methods The 36 healthy female Wistar rats were randomly divided into the normal control group (n=6), and model group, Chinese medicine treated group and saline control group (all n=10). All animals in the model group, Chinese medicine treated group and saline control group were treated with group given L-thyroxine intraperitoneal injection for 42 days to establish the animal model of hyperthyroid myopathy. The animals of the Chinese medicine treated group were treated with Xiaoyngqiangjitang for 30 days after L-thyroxine intraperitoneal injection. The enzyme activity of AchE and ultrastructure of motor end-plate were observed by light and electron microscopes.Results The enzyme activity and content in the group of hyperthyroid myopathy was decreased, the reaction products of AchE located in synapse became weaker and distributed heterogeneously, the junction infolding of motor end-plate became smaller and shorter, the mitochondria in axon terminal became vacuolated. After given Chinese medicine, the enzyme activity and content increased, the junction folding, the mitochondria showed normal ultrastructural appearance.Conclusion Xiaoyingqiangjitang can improve the function of skeletal muscle in hyperthyroid myopathy by recovering the enzyme activity of AchE and ultrastructures of motor end-plate.

Key words: Xiaoyingqiangjitang, skeletal muscles, acetylcholin esterase (AchE), motor end-plate, rat