摘要
The anatomical plan of adult muscle innervation is relatively simple： a given muscle comprises several motor units, each constituted by one motor neuron and the muscle fibers that it innervates; moreover, every muscle fiber is innervated by only one axonal terminal. In other words, motor units have separate, although intermingled, territories of inner- vation （Figure 1D）. In striking contrast, the anatomical organization is different at birth, when every muscle fiber is innervated by several nerve terminals belonging to different motor neurons, a condition known as ＂polyneuronal inner- vation＂, with the consequence that motor units have larger and overlapped territories of innervation （Figure 1A） （Tapia and Lichtman, 2012）. Soon after birth, redundant nerve ter- minals are progressively eliminated in a couple of weeks in rodents, and muscle fibers acquire their mature mononeu- ronal innervation. The same process occurs again in the adult muscle during reinnervation after nerve damage, when a transient period of polyneuronal innervation involves a good fraction of the fibers （Rich and Lichtman, 1989;
The anatomical plan of adult muscle innervation is relatively simple： a given muscle comprises several motor units, each constituted by one motor neuron and the muscle fibers that it innervates; moreover, every muscle fiber is innervated by only one axonal terminal. In other words, motor units have separate, although intermingled, territories of inner- vation （Figure 1D）. In striking contrast, the anatomical organization is different at birth, when every muscle fiber is innervated by several nerve terminals belonging to different motor neurons, a condition known as ＂polyneuronal inner- vation＂, with the consequence that motor units have larger and overlapped territories of innervation （Figure 1A） （Tapia and Lichtman, 2012）. Soon after birth, redundant nerve ter- minals are progressively eliminated in a couple of weeks in rodents, and muscle fibers acquire their mature mononeu- ronal innervation. The same process occurs again in the adult muscle during reinnervation after nerve damage, when a transient period of polyneuronal innervation involves a good fraction of the fibers （Rich and Lichtman, 1989;
