Abstract
The acetylcholinesterase (AChE) activity at the myotendinous junction (MTJ) in several skeletal muscles of limbs and trunks of adult rats and in M. soleus and M. gastrocnemius of newborn rats with or without denervation of sciatic nerves was studied under a light microscope and an electron microscope. Under an electron microscope the AChE activity at the MTJ was detected in the lamina rara. In M, soleus and M. rectus abdominis of adult rats nearly all fibers exhibited AChE activity and in other muscles of adult rats a few fibers exhibited the activity. In M. gastrocnemius of newborn rats the percentage of AChE-positive MTJ was higher than that of adult rats. As they grew the activity gradually decreased. There were AChE-positive and AChE-negative MTJs in muscle. The Z lines of the muscle fiber, which had AChE-positive MTJ, were wider than those of the fiber, which had AChE-negative MTJ. In the denervated muscles, the AChE activity at the MTJ was detected three weeks after the denervation in adult rats and one month after the denervation in newborn rats. In the atrophic muscles the AChE activity could not be detected under a light microscope, but was detected slightly under an electron microscope. The present results suggest that AChE activity is detected at the MTJ in the red muscle fiber and the enzyme seemed to be myogenic.
