EFFECT OF DENERVATION ON SKELETAL MUSCLE DEVELOPMENT OF POSTNATAL RATS / 体力科学

ABSTRACT

At early stage of rats after birth, each innervation muscle fiber is supplied by two or more motor axones which converge on to a single end-plate and become one single axon in future. And undifferentiated cells frequently observed in the interspace among muscle fibers. About 70% of number of total muscle fibers in soleus developed in 21st day after birth.<BR>Effect of denervation on the process of muscle development is studied in this paper. Left saiatic nerve of the rats was cut at 1st, 7th, 14th, and 21st day after birth. After 2 and 4 weeks, soleus and extensor digitorum longus muscle of both legs were dissected. Right side muscles used as control. Each muscle was cut transversely at the muscle belly and quickly frozen. Frozen sections, about 10 pm thick, were stained with hematoxylin eosin and other histochemical agents. Many optical micrographs of 50 or 100 magnifications were obtained from one cross-sectioned specimen. Number of muscle fibers were calculated on combined micrographs.<BR>The results were as follows (1) At 2 and 4 weeks after denervation, percentage loss of muscle weight was always higher than the loss of muscle cross-sectional area. At 2 and 4 weeks after denervation, the muscle weights were reduced to 45-80% and 70-90% of the control. And denervation muscle weights highly reduced in order that of let, 7th, , 14th and 21st eray rate after birth (2) At 2 and 4 weeks after denervation, number of soleus muscle fibers were reduced to 20-50% and 50-70% of the control. (3) At 2 weeks after denervation the reduction of number of muscle fibers of 1st day old rats was smaller than that of 7 days old rats.<BR>First and second results suggest that muscle development is certainly influenced by neurotrophic foctors. But from third result it is possible to think that muscle development at 1st day old rats is influenced by inheritfactors of the muscle.