Regulation of postnatal growth of motor end plates in rat soleus muscle.

The question of whether or not postnatal growth in the length of end-plate acetylcholinesterase plaques in rat soleus muscle is controlled by the nerve or by the muscle was studied. When muscles with intact innervation were tenotomized in young rats, the muscles failed to grow in length and diameter and the end-plate esterase plaques remained short when the animals attained adulthood. When muscles in young rats were denervated the fibers also failed to grow in diameter and end-plate esterase plaques failed to attain the length of control plaques in normal innervated muscle. We conclude that growth of postnatal muscle fiber is an important determinant of end plate and motor terminal growth.