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pp.28-36
The aim of this study was to identify the effect of suspension unloading (SU) and electrical stimulation upon the development of neonatal muscular system. For this study, the neonatal rats were randomly divided into three groups: a control group, an experimental group I, and an experimental group II. The SU for experimental group I and II was applied from postnatal day (PD) 5 to PD 30. The electrical stimulation for soleus muscle of experimental group IIwas applied from PD 16 to PD 30 using neuromuscular electrical stimulation (NMES), which gave isometric contraction with 10 pps for 30 minutes twice a day. In order to observe the effect of SU and ES, this study observed myocyte enhancer factor 2C (MEF2C) and vascular endothelial growth factor (VEGF) immunoreactivity in the soleus muscles at PD 15 and PD 30. In addition, the motor behavior test was performed through footprint analysis at PD 30. The following is the result. At PD 15, the soleus muscles of experimental group Iand II had significantly lower MEF2C, VEGF immunoreactivity than the control group. It proved that microgravity conditions restricted the development of the skeletal muscle cells at PD 15. At PD 30, soleus muscles of the control group and experimental group II had significantly higher MEF2C, VEGF, immunoreactivity than experimental group I. It proved that the NMES facilitated the development of the skeletal muscle cells. At PD 30, it showed that SU caused the decrease in stride length of parameter of gait analysis and an increase in toe-out angle, and that the NMES decreased these variations. These results suggest that weight bearing during neonatal developmental period is essential for muscular development. They also reveal that NMES can encourage the development of muscular systems by fully supplementing the effect of weight bearing, which is an essential factor in the neonatal developmental process.
